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  • ASP.NET Hosting :: ASP.NET File Upload Control

    - by mbridge
    The asp.net FileUpload control allows a user to browse and upload files to the web server. From developers perspective, it is as simple as dragging and dropping the FileUpload control to the aspx page. An extra control, like a Button control, or some other control is needed, to actually save the file. <asp:FileUploadID="FileUpload1"runat="server"/> <asp:ButtonID="B1"runat="server"Text="Save"OnClick="B1_Click"/> By default, the FileUpload control allows a maximum of 4MB file to be uploaded and the execution timeout is 110 seconds. These properties can be changed from within the web.config file’s httpRuntime section. The maxRequestLength property determines the maximum file size that can be uploaded. The executionTimeout property determines the maximum time for execution. <httpRuntimemaxRequestLength="8192"executionTimeout="220"/> From code behind, the mime type, size of the file, file name and the extension of the file can be obtained. The maximum file size that can be uploaded can be obtained and modified using the System.Web.Configuration.HttpRuntimeSection class. Files can be alternatively saved using the System.IO.HttpFileCollection class. This collection class can be populated using the Request.Files property. The collection contains HttpPostedFile class which contains a reference to the class. using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using System.IO; using System.Configuration; using System.Web.Configuration;   namespace WebApplication1 {     public partial class WebControls : System.Web.UI.Page     {         protected void Page_Load(object sender, EventArgs e)         {         }           //Using FileUpload control to upload and save files         protected void B1_Click(object sender, EventArgs e)         {             if (FileUpload1.HasFile && FileUpload1.PostedFile.ContentLength > 0)             {                 //mime type of the uploaded file                 string mimeType = FileUpload1.PostedFile.ContentType;                   //size of the uploaded file                 int size = FileUpload1.PostedFile.ContentLength; // bytes                   //extension of the uploaded file                 string extension = System.IO.Path.GetExtension(FileUpload1.FileName);                                  //save file                 string path = Server.MapPath("path");                                 FileUpload1.SaveAs(path + FileUpload1.FileName);                              }             //maximum file size allowed             HttpRuntimeSection rt = new HttpRuntimeSection();             rt.MaxRequestLength = rt.MaxRequestLength * 2;             int length = rt.MaxRequestLength;                     //execution timeout             TimeSpan ts = rt.ExecutionTimeout;             double secomds = ts.TotalSeconds;           }           //Using Request.Files to save files         private void AltSaveFile()         {             HttpFileCollection coll = Request.Files;             for (int i = 0; i < coll.Count; i++)             {                 HttpPostedFile file = coll[i];                   if (file.ContentLength > 0)                     ;//do something             }         }     } }

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  • Anatomy of a .NET Assembly - Signature encodings

    - by Simon Cooper
    If you've just joined this series, I highly recommend you read the previous posts in this series, starting here, or at least these posts, covering the CLR metadata tables. Before we look at custom attribute encoding, we first need to have a brief look at how signatures are encoded in an assembly in general. Signature types There are several types of signatures in an assembly, all of which share a common base representation, and are all stored as binary blobs in the #Blob heap, referenced by an offset from various metadata tables. The types of signatures are: Method definition and method reference signatures. Field signatures Property signatures Method local variables. These are referenced from the StandAloneSig table, which is then referenced by method body headers. Generic type specifications. These represent a particular instantiation of a generic type. Generic method specifications. Similarly, these represent a particular instantiation of a generic method. All these signatures share the same underlying mechanism to represent a type Representing a type All metadata signatures are based around the ELEMENT_TYPE structure. This assigns a number to each 'built-in' type in the framework; for example, Uint16 is 0x07, String is 0x0e, and Object is 0x1c. Byte codes are also used to indicate SzArrays, multi-dimensional arrays, custom types, and generic type and method variables. However, these require some further information. Firstly, custom types (ie not one of the built-in types). These require you to specify the 4-byte TypeDefOrRef coded token after the CLASS (0x12) or VALUETYPE (0x11) element type. This 4-byte value is stored in a compressed format before being written out to disk (for more excruciating details, you can refer to the CLI specification). SzArrays simply have the array item type after the SZARRAY byte (0x1d). Multidimensional arrays follow the ARRAY element type with a series of compressed integers indicating the number of dimensions, and the size and lower bound of each dimension. Generic variables are simply followed by the index of the generic variable they refer to. There are other additions as well, for example, a specific byte value indicates a method parameter passed by reference (BYREF), and other values indicating custom modifiers. Some examples... To demonstrate, here's a few examples and what the resulting blobs in the #Blob heap will look like. Each name in capitals corresponds to a particular byte value in the ELEMENT_TYPE or CALLCONV structure, and coded tokens to custom types are represented by the type name in curly brackets. A simple field: int intField; FIELD I4 A field of an array of a generic type parameter (assuming T is the first generic parameter of the containing type): T[] genArrayField FIELD SZARRAY VAR 0 An instance method signature (note how the number of parameters does not include the return type): instance string MyMethod(MyType, int&, bool[][]); HASTHIS DEFAULT 3 STRING CLASS {MyType} BYREF I4 SZARRAY SZARRAY BOOLEAN A generic type instantiation: MyGenericType<MyType, MyStruct> GENERICINST CLASS {MyGenericType} 2 CLASS {MyType} VALUETYPE {MyStruct} For more complicated examples, in the following C# type declaration: GenericType<T> : GenericBaseType<object[], T, GenericType<T>> { ... } the Extends field of the TypeDef for GenericType will point to a TypeSpec with the following blob: GENERICINST CLASS {GenericBaseType} 3 SZARRAY OBJECT VAR 0 GENERICINST CLASS {GenericType} 1 VAR 0 And a static generic method signature (generic parameters on types are referenced using VAR, generic parameters on methods using MVAR): TResult[] GenericMethod<TInput, TResult>( TInput, System.Converter<TInput, TOutput>); GENERIC 2 2 SZARRAY MVAR 1 MVAR 0 GENERICINST CLASS {System.Converter} 2 MVAR 0 MVAR 1 As you can see, complicated signatures are recursively built up out of quite simple building blocks to represent all the possible variations in a .NET assembly. Now we've looked at the basics of normal method signatures, in my next post I'll look at custom attribute application signatures, and how they are different to normal signatures.

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  • ADF Seeded Customizations in JDeveloper 11.1.2.1

    - by Dmitry Nefedkin
    For the ADF training I needed a demo application that shows ADF seeded customizations functionality. I’m using the latest JDeveloper 11.1.2.1, so I decided to download the “Customizing and Personalizing an ADF Application” completed tutorial application available here I’ve downloaded and unzipped the CustomizeApp.zip and opened the CustomizeApp.jws in the JDeveloper 11.1.2.1 using the Customization Role. The result was the following: MDS-00036 “Cannot instantiate the class oracle.model.mycompany.SiteCC”. I thought: “OK, that’s because SiteCC class is not accessible to JDeveloper classloader, I should jar it and put to the <JDEVELOPER_HOME> \jdev\lib\patches like I did in JDeveloper 11.1.1.5 and ealier”.  No way, it JDeveloper 11.1.2 we do not have this patches directory at all! It seems that is because of the new architecture of the JDeveloper plugins based on OSGi.   I looked through the tutorial and have not found any step related to the jar–ing the SiteCC class and moving it to the specific directory.  So, JDeveloper 11.1.2  is smart enough to find my customization class and add it to the classpath without any specific actions from my side.  But why am I getting this “cannot instantiate the class” error?I’ve checked at the the full path to my CustomizeApp.jws  - c:\temp\ADF personalizations\CustomizeApp\CustomizeApp.jws  and noticed the space in the name of the directory.  Was it the root cause of the issue?  Yes!  I’ve renamed the ADF personalizations folder to pers, opened the c:\temp\pers\CustomizeApp\CustomizeApp.jws,  and received the expected behaviour: So, be aware of the spaces in the paths when working with JDeveloper…

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  • Why enumerator structs are a really bad idea

    - by Simon Cooper
    If you've ever poked around the .NET class libraries in Reflector, I'm sure you would have noticed that the generic collection classes all have implementations of their IEnumerator as a struct rather than a class. As you will see, this design decision has some rather unfortunate side effects... As is generally known in the .NET world, mutable structs are a Very Bad Idea; and there are several other blogs around explaining this (Eric Lippert's blog post explains the problem quite well). In the BCL, the generic collection enumerators are all mutable structs, as they need to keep track of where they are in the collection. This bit me quite hard when I was coding a wrapper around a LinkedList<int>.Enumerator. It boils down to this code: sealed class EnumeratorWrapper : IEnumerator<int> { private readonly LinkedList<int>.Enumerator m_Enumerator; public EnumeratorWrapper(LinkedList<int> linkedList) { m_Enumerator = linkedList.GetEnumerator(); } public int Current { get { return m_Enumerator.Current; } } object System.Collections.IEnumerator.Current { get { return Current; } } public bool MoveNext() { return m_Enumerator.MoveNext(); } public void Reset() { ((System.Collections.IEnumerator)m_Enumerator).Reset(); } public void Dispose() { m_Enumerator.Dispose(); } } The key line here is the MoveNext method. When I initially coded this, I thought that the call to m_Enumerator.MoveNext() would alter the enumerator state in the m_Enumerator class variable and so the enumeration would proceed in an orderly fashion through the collection. However, when I ran this code it went into an infinite loop - the m_Enumerator.MoveNext() call wasn't actually changing the state in the m_Enumerator variable at all, and my code was looping forever on the first collection element. It was only after disassembling that method that I found out what was going on The MoveNext method above results in the following IL: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000, [1] valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator CS$0$0001) L_0000: nop L_0001: ldarg.0 L_0002: ldfld valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: stloc.1 L_0008: ldloca.s CS$0$0001 L_000a: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000f: stloc.0 L_0010: br.s L_0012 L_0012: ldloc.0 L_0013: ret } Here, the important line is 0002 - m_Enumerator is accessed using the ldfld operator, which does the following: Finds the value of a field in the object whose reference is currently on the evaluation stack. So, what the MoveNext method is doing is the following: public bool MoveNext() { LinkedList<int>.Enumerator CS$0$0001 = this.m_Enumerator; bool CS$1$0000 = CS$0$0001.MoveNext(); return CS$1$0000; } The enumerator instance being modified by the call to MoveNext is the one stored in the CS$0$0001 variable on the stack, and not the one in the EnumeratorWrapper class instance. Hence why the state of m_Enumerator wasn't getting updated. Hmm, ok. Well, why is it doing this? If you have a read of Eric Lippert's blog post about this issue, you'll notice he quotes a few sections of the C# spec. In particular, 7.5.4: ...if the field is readonly and the reference occurs outside an instance constructor of the class in which the field is declared, then the result is a value, namely the value of the field I in the object referenced by E. And my m_Enumerator field is readonly! Indeed, if I remove the readonly from the class variable then the problem goes away, and the code works as expected. The IL confirms this: .method public hidebysig newslot virtual final instance bool MoveNext() cil managed { .maxstack 1 .locals init ( [0] bool CS$1$0000) L_0000: nop L_0001: ldarg.0 L_0002: ldflda valuetype [System]System.Collections.Generic.LinkedList`1/Enumerator EnumeratorWrapper::m_Enumerator L_0007: call instance bool [System]System.Collections.Generic.LinkedList`1/Enumerator::MoveNext() L_000c: stloc.0 L_000d: br.s L_000f L_000f: ldloc.0 L_0010: ret } Notice on line 0002, instead of the ldfld we had before, we've got a ldflda, which does this: Finds the address of a field in the object whose reference is currently on the evaluation stack. Instead of loading the value, we're loading the address of the m_Enumerator field. So now the call to MoveNext modifies the enumerator stored in the class rather than on the stack, and everything works as expected. Previously, I had thought enumerator structs were an odd but interesting feature of the BCL that I had used in the past to do linked list slices. However, effects like this only underline how dangerous mutable structs are, and I'm at a loss to explain why the enumerators were implemented as structs in the first place. (interestingly, the SortedList<TKey, TValue> enumerator is a struct but is private, which makes it even more odd - the only way it can be accessed is as a boxed IEnumerator!). I would love to hear people's theories as to why the enumerators are implemented in such a fashion. And bonus points if you can explain why LinkedList<int>.Enumerator.Reset is an explicit implementation but Dispose is implicit... Note to self: never ever ever code a mutable struct.

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  • Date Time Format in RUBY

    - by Madhan ayyasamy
    The following snippets is very useful when we render views dates in various format in ruby on rails."Format meaning:  %a - The abbreviated weekday name (``Sun'')  %A - The  full  weekday  name (``Sunday'')  %b - The abbreviated month name (``Jan'')  %B - The  full  month  name (``January'')  %c - The preferred local date and time representation  %d - Day of the month (01..31)  %H - Hour of the day, 24-hour clock (00..23)  %I - Hour of the day, 12-hour clock (01..12)  %j - Day of the year (001..366)  %m - Month of the year (01..12)  %M - Minute of the hour (00..59)  %p - Meridian indicator (``AM''  or  ``PM'')  %S - Second of the minute (00..60)  %U - Week  number  of the current year,          starting with the first Sunday as the first          day of the first week (00..53)  %W - Week  number  of the current year,          starting with the first Monday as the first          day of the first week (00..53)  %w - Day of the week (Sunday is 0, 0..6)  %x - Preferred representation for the date alone, no time  %X - Preferred representation for the time alone, no date  %y - Year without a century (00..99)  %Y - Year with century  %Z - Time zone name  %% - Literal ``%'' character   t = Time.now   t.strftime("Printed on %m/%d/%Y")   #=> "Printed on 04/09/2003"   t.strftime("at %I:%M%p")            #=> "at 08:56AM""Have a great day!

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  • Informed TDD &ndash; Kata &ldquo;To Roman Numerals&rdquo;

    - by Ralf Westphal
    Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/05/28/informed-tdd-ndash-kata-ldquoto-roman-numeralsrdquo.aspxIn a comment on my article on what I call Informed TDD (ITDD) reader gustav asked how this approach would apply to the kata “To Roman Numerals”. And whether ITDD wasn´t a violation of TDD´s principle of leaving out “advanced topics like mocks”. I like to respond with this article to his questions. There´s more to say than fits into a commentary. Mocks and TDD I don´t see in how far TDD is avoiding or opposed to mocks. TDD and mocks are orthogonal. TDD is about pocess, mocks are about structure and costs. Maybe by moving forward in tiny red+green+refactor steps less need arises for mocks. But then… if the functionality you need to implement requires “expensive” resource access you can´t avoid using mocks. Because you don´t want to constantly run all your tests against the real resource. True, in ITDD mocks seem to be in almost inflationary use. That´s not what you usually see in TDD demonstrations. However, there´s a reason for that as I tried to explain. I don´t use mocks as proxies for “expensive” resource. Rather they are stand-ins for functionality not yet implemented. They allow me to get a test green on a high level of abstraction. That way I can move forward in a top-down fashion. But if you think of mocks as “advanced” or if you don´t want to use a tool like JustMock, then you don´t need to use mocks. You just need to stand the sight of red tests for a little longer ;-) Let me show you what I mean by that by doing a kata. ITDD for “To Roman Numerals” gustav asked for the kata “To Roman Numerals”. I won´t explain the requirements again. You can find descriptions and TDD demonstrations all over the internet, like this one from Corey Haines. Now here is, how I would do this kata differently. 1. Analyse A demonstration of TDD should never skip the analysis phase. It should be made explicit. The requirements should be formalized and acceptance test cases should be compiled. “Formalization” in this case to me means describing the API of the required functionality. “[D]esign a program to work with Roman numerals” like written in this “requirement document” is not enough to start software development. Coding should only begin, if the interface between the “system under development” and its context is clear. If this interface is not readily recognizable from the requirements, it has to be developed first. Exploration of interface alternatives might be in order. It might be necessary to show several interface mock-ups to the customer – even if that´s you fellow developer. Designing the interface is a task of it´s own. It should not be mixed with implementing the required functionality behind the interface. Unfortunately, though, this happens quite often in TDD demonstrations. TDD is used to explore the API and implement it at the same time. To me that´s a violation of the Single Responsibility Principle (SRP) which not only should hold for software functional units but also for tasks or activities. In the case of this kata the API fortunately is obvious. Just one function is needed: string ToRoman(int arabic). And it lives in a class ArabicRomanConversions. Now what about acceptance test cases? There are hardly any stated in the kata descriptions. Roman numerals are explained, but no specific test cases from the point of view of a customer. So I just “invent” some acceptance test cases by picking roman numerals from a wikipedia article. They are supposed to be just “typical examples” without special meaning. Given the acceptance test cases I then try to develop an understanding of the problem domain. I´ll spare you that. The domain is trivial and is explain in almost all kata descriptions. How roman numerals are built is not difficult to understand. What´s more difficult, though, might be to find an efficient solution to convert into them automatically. 2. Solve The usual TDD demonstration skips a solution finding phase. Like the interface exploration it´s mixed in with the implementation. But I don´t think this is how it should be done. I even think this is not how it really works for the people demonstrating TDD. They´re simplifying their true software development process because they want to show a streamlined TDD process. I doubt this is helping anybody. Before you code you better have a plan what to code. This does not mean you have to do “Big Design Up-Front”. It just means: Have a clear picture of the logical solution in your head before you start to build a physical solution (code). Evidently such a solution can only be as good as your understanding of the problem. If that´s limited your solution will be limited, too. Fortunately, in the case of this kata your understanding does not need to be limited. Thus the logical solution does not need to be limited or preliminary or tentative. That does not mean you need to know every line of code in advance. It just means you know the rough structure of your implementation beforehand. Because it should mirror the process described by the logical or conceptual solution. Here´s my solution approach: The arabic “encoding” of numbers represents them as an ordered set of powers of 10. Each digit is a factor to multiply a power of ten with. The “encoding” 123 is the short form for a set like this: {1*10^2, 2*10^1, 3*10^0}. And the number is the sum of the set members. The roman “encoding” is different. There is no base (like 10 for arabic numbers), there are just digits of different value, and they have to be written in descending order. The “encoding” XVI is short for [10, 5, 1]. And the number is still the sum of the members of this list. The roman “encoding” thus is simpler than the arabic. Each “digit” can be taken at face value. No multiplication with a base required. But what about IV which looks like a contradiction to the above rule? It is not – if you accept roman “digits” not to be limited to be single characters only. Usually I, V, X, L, C, D, M are viewed as “digits”, and IV, IX etc. are viewed as nuisances preventing a simple solution. All looks different, though, once IV, IX etc. are taken as “digits”. Then MCMLIV is just a sum: M+CM+L+IV which is 1000+900+50+4. Whereas before it would have been understood as M-C+M+L-I+V – which is more difficult because here some “digits” get subtracted. Here´s the list of roman “digits” with their values: {1, I}, {4, IV}, {5, V}, {9, IX}, {10, X}, {40, XL}, {50, L}, {90, XC}, {100, C}, {400, CD}, {500, D}, {900, CM}, {1000, M} Since I take IV, IX etc. as “digits” translating an arabic number becomes trivial. I just need to find the values of the roman “digits” making up the number, e.g. 1954 is made up of 1000, 900, 50, and 4. I call those “digits” factors. If I move from the highest factor (M=1000) to the lowest (I=1) then translation is a two phase process: Find all the factors Translate the factors found Compile the roman representation Translation is just a look-up. Finding, though, needs some calculation: Find the highest remaining factor fitting in the value Remember and subtract it from the value Repeat with remaining value and remaining factors Please note: This is just an algorithm. It´s not code, even though it might be close. Being so close to code in my solution approach is due to the triviality of the problem. In more realistic examples the conceptual solution would be on a higher level of abstraction. With this solution in hand I finally can do what TDD advocates: find and prioritize test cases. As I can see from the small process description above, there are two aspects to test: Test the translation Test the compilation Test finding the factors Testing the translation primarily means to check if the map of factors and digits is comprehensive. That´s simple, even though it might be tedious. Testing the compilation is trivial. Testing factor finding, though, is a tad more complicated. I can think of several steps: First check, if an arabic number equal to a factor is processed correctly (e.g. 1000=M). Then check if an arabic number consisting of two consecutive factors (e.g. 1900=[M,CM]) is processed correctly. Then check, if a number consisting of the same factor twice is processed correctly (e.g. 2000=[M,M]). Finally check, if an arabic number consisting of non-consecutive factors (e.g. 1400=[M,CD]) is processed correctly. I feel I can start an implementation now. If something becomes more complicated than expected I can slow down and repeat this process. 3. Implement First I write a test for the acceptance test cases. It´s red because there´s no implementation even of the API. That´s in conformance with “TDD lore”, I´d say: Next I implement the API: The acceptance test now is formally correct, but still red of course. This will not change even now that I zoom in. Because my goal is not to most quickly satisfy these tests, but to implement my solution in a stepwise manner. That I do by “faking” it: I just “assume” three functions to represent the transformation process of my solution: My hypothesis is that those three functions in conjunction produce correct results on the API-level. I just have to implement them correctly. That´s what I´m trying now – one by one. I start with a simple “detail function”: Translate(). And I start with all the test cases in the obvious equivalence partition: As you can see I dare to test a private method. Yes. That´s a white box test. But as you´ll see it won´t make my tests brittle. It serves a purpose right here and now: it lets me focus on getting one aspect of my solution right. Here´s the implementation to satisfy the test: It´s as simple as possible. Right how TDD wants me to do it: KISS. Now for the second equivalence partition: translating multiple factors. (It´a pattern: if you need to do something repeatedly separate the tests for doing it once and doing it multiple times.) In this partition I just need a single test case, I guess. Stepping up from a single translation to multiple translations is no rocket science: Usually I would have implemented the final code right away. Splitting it in two steps is just for “educational purposes” here. How small your implementation steps are is a matter of your programming competency. Some “see” the final code right away before their mental eye – others need to work their way towards it. Having two tests I find more important. Now for the next low hanging fruit: compilation. It´s even simpler than translation. A single test is enough, I guess. And normally I would not even have bothered to write that one, because the implementation is so simple. I don´t need to test .NET framework functionality. But again: if it serves the educational purpose… Finally the most complicated part of the solution: finding the factors. There are several equivalence partitions. But still I decide to write just a single test, since the structure of the test data is the same for all partitions: Again, I´m faking the implementation first: I focus on just the first test case. No looping yet. Faking lets me stay on a high level of abstraction. I can write down the implementation of the solution without bothering myself with details of how to actually accomplish the feat. That´s left for a drill down with a test of the fake function: There are two main equivalence partitions, I guess: either the first factor is appropriate or some next. The implementation seems easy. Both test cases are green. (Of course this only works on the premise that there´s always a matching factor. Which is the case since the smallest factor is 1.) And the first of the equivalence partitions on the higher level also is satisfied: Great, I can move on. Now for more than a single factor: Interestingly not just one test becomes green now, but all of them. Great! You might say, then I must have done not the simplest thing possible. And I would reply: I don´t care. I did the most obvious thing. But I also find this loop very simple. Even simpler than a recursion of which I had thought briefly during the problem solving phase. And by the way: Also the acceptance tests went green: Mission accomplished. At least functionality wise. Now I´ve to tidy up things a bit. TDD calls for refactoring. Not uch refactoring is needed, because I wrote the code in top-down fashion. I faked it until I made it. I endured red tests on higher levels while lower levels weren´t perfected yet. But this way I saved myself from refactoring tediousness. At the end, though, some refactoring is required. But maybe in a different way than you would expect. That´s why I rather call it “cleanup”. First I remove duplication. There are two places where factors are defined: in Translate() and in Find_factors(). So I factor the map out into a class constant. Which leads to a small conversion in Find_factors(): And now for the big cleanup: I remove all tests of private methods. They are scaffolding tests to me. They only have temporary value. They are brittle. Only acceptance tests need to remain. However, I carry over the single “digit” tests from Translate() to the acceptance test. I find them valuable to keep, since the other acceptance tests only exercise a subset of all roman “digits”. This then is my final test class: And this is the final production code: Test coverage as reported by NCrunch is 100%: Reflexion Is this the smallest possible code base for this kata? Sure not. You´ll find more concise solutions on the internet. But LOC are of relatively little concern – as long as I can understand the code quickly. So called “elegant” code, however, often is not easy to understand. The same goes for KISS code – especially if left unrefactored, as it is often the case. That´s why I progressed from requirements to final code the way I did. I first understood and solved the problem on a conceptual level. Then I implemented it top down according to my design. I also could have implemented it bottom-up, since I knew some bottom of the solution. That´s the leaves of the functional decomposition tree. Where things became fuzzy, since the design did not cover any more details as with Find_factors(), I repeated the process in the small, so to speak: fake some top level, endure red high level tests, while first solving a simpler problem. Using scaffolding tests (to be thrown away at the end) brought two advantages: Encapsulation of the implementation details was not compromised. Naturally private methods could stay private. I did not need to make them internal or public just to be able to test them. I was able to write focused tests for small aspects of the solution. No need to test everything through the solution root, the API. The bottom line thus for me is: Informed TDD produces cleaner code in a systematic way. It conforms to core principles of programming: Single Responsibility Principle and/or Separation of Concerns. Distinct roles in development – being a researcher, being an engineer, being a craftsman – are represented as different phases. First find what, what there is. Then devise a solution. Then code the solution, manifest the solution in code. Writing tests first is a good practice. But it should not be taken dogmatic. And above all it should not be overloaded with purposes. And finally: moving from top to bottom through a design produces refactored code right away. Clean code thus almost is inevitable – and not left to a refactoring step at the end which is skipped often for different reasons.   PS: Yes, I have done this kata several times. But that has only an impact on the time needed for phases 1 and 2. I won´t skip them because of that. And there are no shortcuts during implementation because of that.

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  • Scala factory pattern returns unusable abstract type

    - by GGGforce
    Please let me know how to make the following bit of code work as intended. The problem is that the Scala compiler doesn't understand that my factory is returning a concrete class, so my object can't be used later. Can TypeTags or type parameters help? Or do I need to refactor the code some other way? I'm (obviously) new to Scala. trait Animal trait DomesticatedAnimal extends Animal trait Pet extends DomesticatedAnimal {var name: String = _} class Wolf extends Animal class Cow extends DomesticatedAnimal class Dog extends Pet object Animal { def apply(aType: String) = { aType match { case "wolf" => new Wolf case "cow" => new Cow case "dog" => new Dog } } } def name(a: Pet, name: String) { a.name = name println(a +"'s name is: " + a.name) } val d = Animal("dog") name(d, "fred") The last line of code fails because the compiler thinks d is an Animal, not a Dog.

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  • Should adapters or wrappers be unit tested?

    - by m3th0dman
    Suppose that I have a class that implements some logic: public MyLogicImpl implements MyLogic { public void myLogicMethod() { //my logic here } } and somewhere else a test class: public MyLogicImplTest { @Test public void testMyLogicMethod() { /test my logic } } I also have: @WebService public MyWebServices class { @Inject private MyLogic myLogic; @WebMethod public void myLogicWebMethod() { myLogic.myLogicMethod(); } } Should there be a test unit for myLogicWebMethod or should the testing for it be handled in integration testing.

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  • Unit testing in Django

    - by acjohnson55
    I'm really struggling to write effective unit tests for a large Django project. I have reasonably good test coverage, but I've come to realize that the tests I've been writing are definitely integration/acceptance tests, not unit tests at all, and I have critical portions of my application that are not being tested effectively. I want to fix this ASAP. Here's my problem. My schema is deeply relational, and heavily time-oriented, giving my model object high internal coupling and lots of state. Many of my model methods query based on time intervals, and I've got a lot of auto_now_add going on in timestamped fields. So take a method that looks like this for example: def summary(self, startTime=None, endTime=None): # ... logic to assign a proper start and end time # if none was provided, probably using datetime.now() objects = self.related_model_set.manager_method.filter(...) return sum(object.key_method(startTime, endTime) for object in objects) How does one approach testing something like this? Here's where I am so far. It occurs to me that the unit testing objective should be given some mocked behavior by key_method on its arguments, is summary correctly filtering/aggregating to produce a correct result? Mocking datetime.now() is straightforward enough, but how can I mock out the rest of the behavior? I could use fixtures, but I've heard pros and cons of using fixtures for building my data (poor maintainability being a con that hits home for me). I could also setup my data through the ORM, but that can be limiting, because then I have to create related objects as well. And the ORM doesn't let you mess with auto_now_add fields manually. Mocking the ORM is another option, but not only is it tricky to mock deeply nested ORM methods, but the logic in the ORM code gets mocked out of the test, and mocking seems to make the test really dependent on the internals and dependencies of the function-under-test. The toughest nuts to crack seem to be the functions like this, that sit on a few layers of models and lower-level functions and are very dependent on the time, even though these functions may not be super complicated. My overall problem is that no matter how I seem to slice it, my tests are looking way more complex than the functions they are testing.

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  • The problems with Avoiding Smurf Naming classes with namespaces

    - by Daniel Koverman
    I pulled the term smurf naming from here (number 21). To save anyone not familiar the trouble, Smurf naming is the act of prefixing a bunch of related classes, variables, etc with a common prefix so you end up with "a SmurfAccountView passes a SmurfAccountDTO to the SmurfAccountController", etc. The solution I've generally heard to this is to make a smurf namespace and drop the smurf prefixes. This has generally served me well, but I'm running into two problems. I'm working with a library with a Configuration class. It could have been called WartmongerConfiguration but it's in the Wartmonger namespace, so it's just called Configuration. I likewise have a Configuration class which could be called SmurfConfiguration, but it is in the Smurf namespace so that would be redundant. There are places in my code where Smurf.Configuration appears alongside Wartmonger.Configuration and typing out fully qualified names is clunky and makes the code less readable. It would be nicer to deal with a SmurfConfiguration and (if it was my code and not a library) WartmongerConfiguration. I have a class called Service in my Smurf namespace which could have been called SmurfService. Service is a facade on top of a complex Smurf library which runs Smurf jobs. SmurfService seems like a better name because Service without the Smurf prefix is so incredibly generic. I can accept that SmurfService was already a generic, useless name and taking away smurf merely made this more apparent. But it could have been named Runner, Launcher, etc and it would still "feel better" to me as SmurfLauncher because I don't know what a Launcher does, but I know what a SmurfLauncher does. You could argue that what a Smurf.Launcher does should be just as apparent as a Smurf.SmurfLauncher, but I could see `Smurf.Launcher being some kind of class related to setup rather than a class that launches smurfs. If there is an open and shut way to deal with either of these that would be great. If not, what are some common practices to mitigate their annoyance?

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  • What naming anti-patterns exist?

    - by Billy ONeal
    There are some names, where if you find yourself reaching for those names, you know you've already messed something up. For example: XxxManager This is bad because a class should describe what the class does. If the most specific word you can come up with for what the class does is "manage," then the class is too big. What other naming anti-patterns exist? EDIT: To clarify, I'm not asking "what names are bad" -- that question is entirely subjective and there's no way to answer it. I'm asking, "what names indicate overall design problems with the system." That is, if you find yourself wanting to call a component Xyz, that probably indicates the component is ill concieved. Also note here that there are exceptions to every rule -- I'm just looking for warning flags for when I really need to stop and rethink a design.

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  • Highlight current page tab [migrated]

    - by Jose David Garcia Llanos
    I am making a website, currently i am setting the highlight tab for current page, a particular page is not highlighting its tab and i have checked the code about 5 times but i cant find anything wrong with it. the website is auto-sal.es Here is the code: style.css body#home a.hometab, body#cars a.cartab, body#feedback a.feedtab, body#contact a.contacttab, body#members a.memberstab {background: #7D0000;} contactus.html <body id="contact"> navigation <ul id="menu"> <li><a href="index.html" target="_self" class="hometab">Home</a></li> <li><a href="cars.html" target="_self" class="cartab">Cars</a></li> <li><a href="feedback.html" target="_self" class="feedtab">Feedback</a></li> <li><a href="contactus.html" target="_self" class="cotacttab">Contact Us</a></li> <li><a href="members.html" target="_self" class="memberstab">Members</a></li> </ul> Again, the issue is that it is not highlighting the tab for contact us

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  • How do I add leaderboard feature of OpenFeint in android?

    - by Avi kumar Manku
    I am developing a game in android, by extending a class with view. I have integrated OpenFeint in it by studying the tutorial provided on the OpenFeint site, but I am not able to add the leaderboard feature in my app. How can I achieve it? My game class is like this public class GameActivity extends Activity { Intent i; Grapic g; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); setContentView(new Grapic(this)); and Grapic is a class which extends view and where scoring is done with touch events.

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  • What source code organization approach helps improve modularity and API/Implementation separation?

    - by Berin Loritsch
    Few languages are as restrictive as Java with file naming standards and project structure. In that language, the file name must match the public class declared in the file, and the file must live in a directory structure matching the class package. I have mixed feelings about that approach. While I never have to guess where a file lives, there's still a lot of empty directories and artificial constraints. There's several languages that define everything about a class in one file, at least by convention. C#, Python (I think), Ruby, Erlang, etc. The commonality in most these languages is that they are object oriented, although that statement can probably be rebuffed (there is one non-OO language in the list already). Finally, there's quite a few languages mostly in the C family that have a separate header and implementation file. For C I think this makes sense, because it is one of the few ways to separate the API interface from implementations. With C it seems that feature is used to promote modularity. Yet, with C++ the way header and implementation files are split seems rather forced. You don't get the same clean API separation that you do with C, and you are forced to include some private details in the header you would rather keep only in the implementation. There's quite a few languages that have a concept that overlaps with interfaces like Java, C#, Go, etc. Some languages use what feels like a hack to provide the same concept like C# using pure virtual abstract classes. Still others don't really have an interface concept and rely on "duck" typing--for example Ruby. Ruby has modules, but those are more along the lines of mixing in behaviors to a class than they are for defining how to interact with a class. In OO terms, interfaces are a powerful way to provide separation between an API client and an API implementation. So to hurry up and ask the question, from a personal experience point of view: Does separation of header and implementation help you write more modular code, or does it get in the way? (it helps to specify the language you are referring to) Does the strict file name to class name scheme of Java help maintainability, or is it unnecessary structure for structure's sake? What would you propose to promote good API/Implementation separation and project maintenance, how would you prefer to do it?

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  • What is the best way to code the XNA Game Server for FPS game?

    - by AgentFire
    I'm writing a FPS XNA game. It gonna be multiplayer so I came up with following: I'm making two different assemblies — one for the game logic and the second for drawing it and the game irrelevant stuff (like rocket trails). The type of the connection is client-server (not peer-to-peer), so every client at first connects to the server and then the game begins. I'm completly decided to use XNA.Framework.Game class for the clients to run their game in window (or fullscreen) and the GameComponent/DrawableGameComponent classes to store the game objects and update&draw them on each frame. Next, I want to get the answer to the question: What should I do on the server side? I got few options: Create my own Game class on the server, which will process all the game logic (only, no graphics). The reason why I am not using the standart Game class is when I call Game.Run() the white window appears and I cant figure out how to get rid of it. Use somehow the original XNA's Game class, which is already has the GameComponent collection and Update event (60 times per second, just what I need). UPDATE: I got more questions: First, what socket mode should I use? TCP or UDP? And how to actually let the client know that this packet is meant to be processed after that one? Second, if I is going to use exacly GameComponent class for the game objects which is stored and process on the server, how to make them to be drawn on the client? Inherit them (while they are combined to an assembly)? Something else?

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  • Detecting HTML5/CSS3 Features using Modernizr

    - by dwahlin
    HTML5, CSS3, and related technologies such as canvas and web sockets bring a lot of useful new features to the table that can take Web applications to the next level. These new technologies allow applications to be built using only HTML, CSS, and JavaScript allowing them to be viewed on a variety of form factors including tablets and phones. Although HTML5 features offer a lot of promise, it’s not realistic to develop applications using the latest technologies without worrying about supporting older browsers in the process. If history has taught us anything it’s that old browsers stick around for years and years which means developers have to deal with backward compatibility issues. This is especially true when deploying applications to the Internet that target the general public. This begs the question, “How do you move forward with HTML5 and CSS3 technologies while gracefully handling unsupported features in older browsers?” Although you can write code by hand to detect different HTML5 and CSS3 features, it’s not always straightforward. For example, to check for canvas support you need to write code similar to the following:   <script> window.onload = function () { if (canvasSupported()) { alert('canvas supported'); } }; function canvasSupported() { var canvas = document.createElement('canvas'); return (canvas.getContext && canvas.getContext('2d')); } </script> If you want to check for local storage support the following check can be made. It’s more involved than it should be due to a bug in older versions of Firefox. <script> window.onload = function () { if (localStorageSupported()) { alert('local storage supported'); } }; function localStorageSupported() { try { return ('localStorage' in window && window['localStorage'] != null); } catch(e) {} return false; } </script> Looking through the previous examples you can see that there’s more than meets the eye when it comes to checking browsers for HTML5 and CSS3 features. It takes a lot of work to test every possible scenario and every version of a given browser. Fortunately, you don’t have to resort to writing custom code to test what HTML5/CSS3 features a given browser supports. By using a script library called Modernizr you can add checks for different HTML5/CSS3 features into your pages with a minimal amount of code on your part. Let’s take a look at some of the key features Modernizr offers.   Getting Started with Modernizr The first time I heard the name “Modernizr” I thought it “modernized” older browsers by added missing functionality. In reality, Modernizr doesn’t actually handle adding missing features or “modernizing” older browsers. The Modernizr website states, “The name Modernizr actually stems from the goal of modernizing our development practices (and ourselves)”. Because it relies on feature detection rather than browser sniffing (a common technique used in the past – that never worked that great), Modernizr definitely provides a more modern way to test features that a browser supports and can even handle loading additional scripts called shims or polyfills that fill in holes that older browsers may have. It’s a great tool to have in your arsenal if you’re a web developer. Modernizr is available at http://modernizr.com. Two different types of scripts are available including a development script and custom production script. To generate a production script, the site provides a custom script generation tool rather than providing a single script that has everything under the sun for HTML5/CSS3 feature detection. Using the script generation tool you can pick the specific test functionality that you need and ignore everything that you don’t need. That way the script is kept as small as possible. An example of the custom script download screen is shown next. Notice that specific CSS3, HTML5, and related feature tests can be selected. Once you’ve downloaded your custom script you can add it into your web page using the standard <script> element and you’re ready to start using Modernizr. <script src="Scripts/Modernizr.js" type="text/javascript"></script>   Modernizr and the HTML Element Once you’ve add a script reference to Modernizr in a page it’ll go to work for you immediately. In fact, by adding the script several different CSS classes will be added to the page’s <html> element at runtime. These classes define what features the browser supports and what features it doesn’t support. Features that aren’t supported get a class name of “no-FeatureName”, for example “no-flexbox”. Features that are supported get a CSS class name based on the feature such as “canvas” or “websockets”. An example of classes added when running a page in Chrome is shown next:   <html class=" js flexbox canvas canvastext webgl no-touch geolocation postmessage websqldatabase indexeddb hashchange history draganddrop websockets rgba hsla multiplebgs backgroundsize borderimage borderradius boxshadow textshadow opacity cssanimations csscolumns cssgradients cssreflections csstransforms csstransforms3d csstransitions fontface generatedcontent video audio localstorage sessionstorage webworkers applicationcache svg inlinesvg smil svgclippaths"> Here’s an example of what the <html> element looks like at runtime with Internet Explorer 9:   <html class=" js no-flexbox canvas canvastext no-webgl no-touch geolocation postmessage no-websqldatabase no-indexeddb hashchange no-history draganddrop no-websockets rgba hsla multiplebgs backgroundsize no-borderimage borderradius boxshadow no-textshadow opacity no-cssanimations no-csscolumns no-cssgradients no-cssreflections csstransforms no-csstransforms3d no-csstransitions fontface generatedcontent video audio localstorage sessionstorage no-webworkers no-applicationcache svg inlinesvg smil svgclippaths">   When using Modernizr it’s a common practice to define an <html> element in your page with a no-js class added as shown next:   <html class="no-js">   You’ll see starter projects such as HTML5 Boilerplate (http://html5boilerplate.com) or Initializr (http://initializr.com) follow this approach (see my previous post for more information on HTML5 Boilerplate). By adding the no-js class it’s easy to tell if a browser has JavaScript enabled or not. If JavaScript is disabled then no-js will stay on the <html> element. If JavaScript is enabled, no-js will be removed by Modernizr and a js class will be added along with other classes that define supported/unsupported features. Working with HTML5 and CSS3 Features You can use the CSS classes added to the <html> element directly in your CSS files to determine what style properties to use based upon the features supported by a given browser. For example, the following CSS can be used to render a box shadow for browsers that support that feature and a simple border for browsers that don’t support the feature: .boxshadow #MyContainer { border: none; -webkit-box-shadow: #666 1px 1px 1px; -moz-box-shadow: #666 1px 1px 1px; } .no-boxshadow #MyContainer { border: 2px solid black; }   If a browser supports box-shadows the boxshadow CSS class will be added to the <html> element by Modernizr. It can then be associated with a given element. This example associates the boxshadow class with a div with an id of MyContainer. If the browser doesn’t support box shadows then the no-boxshadow class will be added to the <html> element and it can be used to render a standard border around the div. This provides a great way to leverage new CSS3 features in supported browsers while providing a graceful fallback for older browsers. In addition to using the CSS classes that Modernizr provides on the <html> element, you also use a global Modernizr object that’s created. This object exposes different properties that can be used to detect the availability of specific HTML5 or CSS3 features. For example, the following code can be used to detect canvas and local storage support. You can see that the code is much simpler than the code shown at the beginning of this post. It also has the added benefit of being tested by a large community of web developers around the world running a variety of browsers.   $(document).ready(function () { if (Modernizr.canvas) { //Add canvas code } if (Modernizr.localstorage) { //Add local storage code } }); The global Modernizr object can also be used to test for the presence of CSS3 features. The following code shows how to test support for border-radius and CSS transforms:   $(document).ready(function () { if (Modernizr.borderradius) { $('#MyDiv').addClass('borderRadiusStyle'); } if (Modernizr.csstransforms) { $('#MyDiv').addClass('transformsStyle'); } });   Several other CSS3 feature tests can be performed such as support for opacity, rgba, text-shadow, CSS animations, CSS transitions, multiple backgrounds, and more. A complete list of supported HTML5 and CSS3 tests that Modernizr supports can be found at http://www.modernizr.com/docs.   Loading Scripts using Modernizr In cases where a browser doesn’t support a specific feature you can either provide a graceful fallback or load a shim/polyfill script to fill in missing functionality where appropriate (more information about shims/polyfills can be found at https://github.com/Modernizr/Modernizr/wiki/HTML5-Cross-Browser-Polyfills). Modernizr has a built-in script loader that can be used to test for a feature and then load a script if the feature isn’t available. The script loader is built-into Modernizr and is also available as a standalone yepnope script (http://yepnopejs.com). It’s extremely easy to get started using the script loader and it can really simplify the process of loading scripts based on the availability of a particular browser feature. To load scripts dynamically you can use Modernizr’s load() function which accepts properties defining the feature to test (test property), the script to load if the test succeeds (yep property), the script to load if the test fails (nope property), and a script to load regardless of if the test succeeds or fails (both property). An example of using load() with these properties is show next: Modernizr.load({ test: Modernizr.canvas, yep: 'html5CanvasAvailable.js’, nope: 'excanvas.js’, both: 'myCustomScript.js' }); In this example Modernizr is used to not only load scripts but also to test for the presence of the canvas feature. If the target browser supports the HTML5 canvas then the html5CanvasAvailable.js script will be loaded along with the myCustomScript.js script (use of the yep property in this example is a bit contrived – it was added simply to demonstrate how the property can be used in the load() function). Otherwise, a polyfill script named excanvas.js will be loaded to add missing canvas functionality for Internet Explorer versions prior to 9. Once excanvas.js is loaded the myCustomScript.js script will be loaded. Because Modernizr handles loading scripts, you can also use it in creative ways. For example, you can use it to load local scripts when a 3rd party Content Delivery Network (CDN) such as one provided by Google or Microsoft is unavailable for whatever reason. The Modernizr documentation provides the following example that demonstrates the process for providing a local fallback for jQuery when a CDN is down:   Modernizr.load([ { load: '//ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.js', complete: function () { if (!window.jQuery) { Modernizr.load('js/libs/jquery-1.6.4.min.js'); } } }, { // This will wait for the fallback to load and // execute if it needs to. load: 'needs-jQuery.js' } ]); This code attempts to load jQuery from the Google CDN first. Once the script is downloaded (or if it fails) the function associated with complete will be called. The function checks to make sure that the jQuery object is available and if it’s not Modernizr is used to load a local jQuery script. After all of that occurs a script named needs-jQuery.js will be loaded. Conclusion If you’re building applications that use some of the latest and greatest features available in HTML5 and CSS3 then Modernizr is an essential tool. By using it you can reduce the amount of custom code required to test for browser features and provide graceful fallbacks or even load shim/polyfill scripts for older browsers to help fill in missing functionality. 

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  • Requesting feedback on my OO design

    - by Prog
    I'm working on an application that creates music by itself. I'm seeking feedback for my OO design so far. This question will focus on one part of the program. The application produces Tune objects, that are the final musical products. Tune is an abstract class with an abstract method play. It has two subclasses: SimpleTune and StructuredTune. SimpleTune owns a Melody and a Progression (chord sequence). It's play implementation plays these two objects simultaneously. StructuredTune owns two Tune instances. It's own play plays the two Tunes one after the other according to a pattern (currently only ABAB). Melody is an abstract class with an abstract play method. It has two subclasses: SimpleMelody and StructuredMelody. SimpleMelody is composed of an array of notes. Invoking play on it plays these notes one after the other. StructuredMelody is composed of an array of Melody objects. Invoking play on it plays these Melodyies one after the other. I think you're starting to see the pattern. Progression is also an abstract class with a play method and two subclasses: SimpleProgression and StructuredProgression, each composed differently and played differently. SimpleProgression owns an array of chords and plays them sequentially. StructuredProgression owns an array of Progressions and it's play implementation plays them sequentially. Every class has a corresponding Generator class. Tune, Melody and Progression are matched with corresponding abstract TuneGenerator, MelodyGenerator and ProgressionGenerator classes, each with an abstract generate method. For example MelodyGenerator defines an abstract Melody generate method. Each of the generators has two subclasses, Simple and Structured. So for example MelodyGenerator has a subclasses SimpleMelodyGenerator, with an implementation of generate that returns a SimpleMelody. (It's important to note that the generate methods encapsulate complex algorithms. They are more than mere factory method. For example SimpleProgressionGenerator.generate() implements an algorithm to compose a series of Chord objects, which are used to instantiate the returned SimpleProgression). Every Structured generator uses another generator internally. It is a Simple generator be default, but in special cases may be a Structured generator. Parts of this design are meant to allow the end-user through the GUI to choose what kind of music is to be created. For example the user can choose between a "simple tune" (SimpleTuneGenerator) and a "full tune" (StructuredTuneGenerator). Other parts of the system aren't subject to direct user-control. What do you think of this design from an OOD perspective? What potential problems do you see with this design? Please share with me your criticism, I'm here to learn. Apart from this, a more specific question: the "every class has a corresponding Generator class" part feels very wrong. However I'm not sure how I could design this differently and achieve the same flexibility. Any ideas?

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  • How to preseed 12.10 desktop when the ubuntu-desktop package is missing?

    - by user183394
    I have been trying to use a preseed file to do PXE booting of a 12.10 desktop. Upon the first boot, I was greeted by a terminal with login prompt. Surprised, I checked the /var/log/installer/syslog but didn't find a trace of desktop installation. Feeling curious, I double-checked the content of the loop mounted iso file, and realized that the ubuntu-desktop package that existed up to 12.04.1 is no longer available. So, the following preseed lines from the Ubuntu preseed example no longer apply: ################################################################################ ### Package selection ### ################################################################################ # Selected packages. tasksel tasksel/first multiselect ubuntu-desktop #tasksel tasksel/first multiselect lamp-server, print-server #tasksel tasksel/first multiselect kubuntu-desktop Given such a situation, is there something that I can specify in the pre-seed file to install the entire default desktop?

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate instance of the extended thread class each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • Turning on collision crashes game

    - by MomentumGaming
    I am getting a null pointer excecption to both my sprite and level. I am working on my mob class, and when I try to move him and the move function is called, the game crashes after checking collision with a null pointer excecption. Taking out the one line that actually checks if the tile located in front of it fixes the problem. Also, if i keep collision ON but don't move the position of the mob (the spider) the game works fine. I will have collision, and the spider appears on the screen, only problem is, getting it to move causes this nasty error that i just can't fix. true Exception in thread "Display" java.lang.NullPointerException at com.apcompsci.game.entity.mob.Mob.collision(Mob.java:67) at com.apcompsci.game.entity.mob.Mob.move(Mob.java:38) at com.apcompsci.game.entity.mob.spider.update(spider.java:58) at com.apcompsci.game.level.Level.update(Level.java:55) at com.apcompsci.game.Game.update(Game.java:128) at com.apcompsci.game.Game.run(Game.java:106) at java.lang.Thread.run(Unknown Source) Here is my renderMob mehtod: public void renderMob(int xp,int yp,Sprite sprite,int flip) { xp -= xOffset; yp-=yOffset; for(int y = 0; y<32; y++) { int ya = y + yp; int ys = y; if(flip == 2||flip == 3)ys = 31-y; for(int x = 0; x<32; x++) { int xa = x + xp; int xs = x; if(flip == 1||flip == 3)xs = 31-x; if(xa < -32 || xa >=width || ya<0||ya>=height) break; if(xa<0) xa =0; int col = sprite.pixels[xs+ys*32]; if(col!= 0x000000) pixels[xa+ya*width] = col; } } } My spider class which determines the sprite and where I control movement, also rendering the spider onto the screen, when I increment ya to move the sprite, I get the crash, but without ya++, it runs flawlessly with a spider sprite on screen: package com.apcompsci.game.entity.mob; import com.apcompsci.game.entity.mob.Mob.Direction; import com.apcompsci.game.graphics.Screen; import com.apcompsci.game.graphics.Sprite; import com.apcompsci.game.level.Level; public class spider extends Mob{ Direction dir; private Sprite sprite; private boolean walking; public spider(int x, int y) { this.x = x <<4; this.y = y <<4; sprite = sprite.spider_forward; } public void update() { int xa = 0, ya = 0; ya++; if(ya<0) { sprite = sprite.spider_forward; dir = Direction.UP; } if(ya>0) { sprite = sprite.spider_back; dir = Direction.DOWN; } if(xa<0) { sprite = sprite.spider_side; dir = Direction.LEFT; } if(xa>0) { sprite = sprite.spider_side; dir = Direction.LEFT; } if(xa!= 0 || ya!= 0) { System.out.println("true"); move(xa,ya); walking = true; } else{ walking = false; } } public void render(Screen screen) { screen.renderMob(x, y, sprite, 0); } } This is th mob class that contains the move() method that is called in the spider class above. This move method calls the collision method. tile and sprite comes up null in the debugger: package com.apcompsci.game.entity.mob; import java.util.ArrayList; import java.util.List; import com.apcompsci.game.entity.Entity; import com.apcompsci.game.entity.projectile.DemiGodProjectile; import com.apcompsci.game.entity.projectile.Projectile; import com.apcompsci.game.graphics.Sprite; public class Mob extends Entity{ protected Sprite sprite; protected boolean moving = false; protected enum Direction { UP,DOWN,LEFT,RIGHT } protected Direction dir; public void move(int xa,int ya) { if(xa != 0 && ya != 0) { move(xa,0); move(0,ya); return; } if(xa>0) dir = Direction.RIGHT; if(xa<0) dir = Direction.LEFT; if(ya>0)dir = Direction.DOWN; if(ya<0)dir = Direction.UP; if(!collision(xa,ya)){ x+= xa; y+=ya; } } public void update() { } public void shoot(int x, int y, double dir) { //dir = Math.toDegrees(dir); Projectile p = new DemiGodProjectile(x, y,dir); level.addProjectile(p); } public boolean collision(int xa,int ya) { boolean solid = false; for(int c = 0; c<4; c++) { int xt = ((x+xa) + c % 2 * 14 - 8 )/16; int yt = ((y+ya) + c / 2 * 12 +3 )/16; if(level.getTile(xt, yt).solid()) solid = true; } return solid; } public void render() { } } Finally, here is the method in which i call the add() method for the spider to add it to the level: protected void loadLevel(String path) { try{ BufferedImage image = ImageIO.read(SpawnLevel.class.getResource(path)); int w = width =image.getWidth(); int h = height = image.getHeight(); tiles = new int[w*h]; image.getRGB(0, 0, w,h, tiles,0, w); } catch(IOException e){ e.printStackTrace(); System.out.println("Exception! Could not load level file!"); } add(new spider(20,45)); } I don't think i need to include the level class but just in case, I have provided a gistHub link for better context. It contains all of the full classes listed above , plus my entity class and maybe another. Thanks for the help if you decide to do so, much appreciated! Also, please tell me if i'm in the wrong section of stackeoverflow, i figured that since this is the gamign section that it belonged but debugging code normally goes into the general section.

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  • Encrypting your SQL Server Passwords in Powershell

    - by laerte
    A couple of months ago, a friend of mine who is now bewitched by the seemingly supernatural abilities of Powershell (+1 for the team) asked me what, initially, appeared to be a trivial question: "Laerte, I do not have the luxury of being able to work with my SQL servers through Windows Authentication, and I need a way to automatically pass my username and password. How would you suggest I do this?" Given that I knew he, like me, was using the SQLPSX modules (an open source project created by Chad Miller; a fantastic library of reusable functions and PowerShell scripts), I merrily replied, "Simply pass the Username and Password in SQLPSX functions". He rather pointed responded: "My friend, I might as well pass: Username-'Me'-password 'NowEverybodyKnowsMyPassword'" As I do have the pleasure of working with Windows Authentication, I had not really thought this situation though yet (and thank goodness I only revealed my temporary ignorance to a friend, and the embarrassment was minimized). After discussing this puzzle with Chad Miller, he showed me some code for saving passwords on SQL Server Tables, which he had demo'd in his Powershell ETL session at Tampa SQL Saturday (and you can download the scripts from here). The solution seemed to be pretty much ready to go, so I showed it to my Authentication-impoverished friend, only to discover that we were only half-way there: "That's almost what I want, but the details need to be stored in my local txt file, together with the names of the servers that I'll actually use the Powershell scripts on. Something like: Server1,UserName,Password Server2,UserName,Password" I thought about it for just a few milliseconds (Ha! Of course I'm not telling you how long it actually took me, I have to do my own marketing, after all) and the solution was finally ready. First , we have to download Library-StringCripto (with many thanks to Steven Hystad), which is composed of two functions: One for encryption and other for decryption, both of which are used to manage the password. If you want to know more about the library, you can see more details in the help functions. Next, we have to create a txt file with your encrypted passwords:$ServerName = "Server1" $UserName = "Login1" $Password = "Senha1" $PasswordToEncrypt = "YourPassword" $UserNameEncrypt = Write-EncryptedString -inputstring $UserName -Password $PasswordToEncrypt $PasswordEncrypt = Write-EncryptedString -inputstring $Password -Password $PasswordToEncrypt "$($Servername),$($UserNameEncrypt),$($PasswordEncrypt)" | Out-File c:\temp\ServersSecurePassword.txt -Append $ServerName = "Server2" $UserName = "Login2" $Password = "senha2" $PasswordToEncrypt = "YourPassword" $UserNameEncrypt = Write-EncryptedString -inputstring $UserName -Password $PasswordToEncrypt $PasswordEncrypt = Write-EncryptedString -inputstring $Password -Password $PasswordToEncrypt "$($Servername),$($UserNameEncrypt),$($PasswordEncrypt)" | Out-File c:\temp\ ServersSecurePassword.txt -Append .And in the c:\temp\ServersSecurePassword.txt file which we've just created, you will find your Username and Password, all neatly encrypted. Let's take a look at what the txt looks like: .and in case you're wondering, Server names, Usernames and Passwords are all separated by commas. Decryption is actually much more simple:Read-EncryptedString -InputString $EncryptString -password "YourPassword" (Just remember that the Password you're trying to decrypt must be exactly the same as the encrypted phrase.) Finally, just to show you how smooth this solution is, let's say I want to use the Invoke-DBMaint function from SQLPSX to perform a checkdb on a system database: it's just a case of split, decrypt and be happy!Get-Content c:\temp\ServerSecurePassword.txt | foreach { [array] $Split = ($_).split(",") Invoke-DBMaint -server $($Split[0]) -UserName (Read-EncryptedString -InputString $Split[1] -password "YourPassword" ) -Password (Read-EncryptedString -InputString $Split[2] -password "YourPassword" ) -Databases "SYSTEM" -Action "CHECK_DB" -ReportOn c:\Temp } This is why I love Powershell.

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  • Where does the term "Front End" come from?

    - by Richard JP Le Guen
    Where does the term "front-end" come from? Is there a particular presentation/talk/job-posting which is regarded as the first use of the term? Is someone credited with coining the term? The Merriam-Webster entry for "front-end" claims the first known use of the term was 1973 but it doesn't seem to provide details about that first known use. Likewise, the Wikipedia page about front and back ends is fairly low quality, and cites very few sources.

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  • When following SRP, how should I deal with validating and saving entities?

    - by Kristof Claes
    I've been reading Clean Code and various online articles about SOLID lately, and the more I read about it, the more I feel like I don't know anything. Let's say I'm building a web application using ASP.NET MVC 3. Let's say I have a UsersController with a Create action like this: public class UsersController : Controller { public ActionResult Create(CreateUserViewModel viewModel) { } } In that action method I want to save a user to the database if the data that was entered is valid. Now, according to the Single Responsibility Principle an object should have a single responsibility, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. Since validation and saving to the database are two separate responsibilities, I guess I should create to separate class to handle them like this: public class UsersController : Controller { private ICreateUserValidator validator; private IUserService service; public UsersController(ICreateUserValidator validator, IUserService service) { this.validator = validator; this.service= service; } public ActionResult Create(CreateUserViewModel viewModel) { ValidationResult result = validator.IsValid(viewModel); if (result.IsValid) { service.CreateUser(viewModel); return RedirectToAction("Index"); } else { foreach (var errorMessage in result.ErrorMessages) { ModelState.AddModelError(String.Empty, errorMessage); } return View(viewModel); } } } That makes some sense to me, but I'm not at all sure that this is the right way to handle things like this. It is for example entirely possible to pass an invalid instance of CreateUserViewModel to the IUserService class. I know I could use the built in DataAnnotations, but what when they aren't enough? Image that my ICreateUserValidator checks the database to see if there already is another user with the same name... Another option is to let the IUserService take care of the validation like this: public class UserService : IUserService { private ICreateUserValidator validator; public UserService(ICreateUserValidator validator) { this.validator = validator; } public ValidationResult CreateUser(CreateUserViewModel viewModel) { var result = validator.IsValid(viewModel); if (result.IsValid) { // Save the user } return result; } } But I feel I'm violating the Single Responsibility Principle here. How should I deal with something like this?

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  • Software development life cycle in the industry

    - by jiewmeng
    I am taking a module called "Requirements Analysis & Design" in a local university. Common module, I'd say (on software development life cycle (SDLC) and UML). But there is a lot of things I wonder if they are actually (strictly) practiced in the industry. For example, will a domain class diagram, an not anything extra (from design class), be strictly the output from Analysis or Discovery phase? I'm sure many times you will think a bit about the technical implementation too? Else you might end up with a design class diagram later that is very different from the original domain class diagram? I also find it hard to remember what diagrams are from Initiation, Discovery, Design etc etc. Plus these phases vary from SDLC to SDLC, I believe? So I usually will create a diagram when I think will be useful. Is it the wrong way?

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  • CSS naming guildlines with elements with multiple classes

    - by ryanzec
    Its seems like there are 2 ways someone can handle naming classes for elements that are designed to have multiple classes. One way would be: <span class="btn btn-success"></span> This is something that twitter bootstrap uses. Another possibility I would think would be: <span class="btn success"></span> It seems like the zurb foundation uses this method. Now the benefits of the first that I can see is that there less chance of outside css interfering with styling as the class name btn-success would not be as common as the class name success. The benefit of the second as I can see is that there is less typing and potential better style reuse. Are there any other benefits/disadvantages of either option and is one of them more popular than the other?

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