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• How can "today's date" be varied for unit testing purposes?

  - by ck

  I use VS2008 targetting .NET 2.0 Framework, and, just in case, no I can't change this :) I have a DateCalculator class. Its method GetNextExpirationDate attempts to determine the next expiration, internally using DateTime.Today as a baseline date. As I was writing unit tests, I realized that I wanted to test GetNextExpirationDate for different 'today' dates. What's the best way to do this? Here are some alternatives I've considered: Expose a property/overloaded method with argument baselineDate and only use it from the unit test. In actual client code, disregard the property/overloaded method in favour of the method that defaults baselineDate to DateTime.Today. I'm reluctant to do this as it makes the public interface of the DateCalculator class awkward. Create a protected field called baselineDate that is internally set to DateTime.Today. When testing, derive a DateCalculatorForTesting from DateCalculator and set baslineDate via the constructor. It keeps the public interface clean, but still isn't great - baselineDate was made protected and a derived class is required, both solely for testing. Use extension methods. I tried this after adding the ExtensionAttribute, then realized it wouldn't work because extension methods can't access private/protected variables. I initially thought this was really quite an elegant solution. :( I'd be interested in hearing what others think.

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• NSMutableDictionary isn't stick around long enough

  - by Sean Danzeiser

  Sorry, beginner here . . . So I create an NSMutableDictionary in my app delegate when the application launches, and then later pass it on to a view controller, as it contains options for the VC like a background image, a url I want to parse, etc. Anyway, i wrote a custom init method for the VC, initWithOptions, where I pass the dictionary on. I'm trying to use this dictionary later on in other methods - so I created a NSMutableDictionary property for my VC and am trying to store the passed options dictionary there. However, when I go to get the contents of that property in later methods, it returns null. If i access it from the init method, it works. heres some sample code: -(id)initWithOptions:(NSMutableDictionary *)options { self = [super init]; if (self) { // Custom initialization self.optionsDict = [[NSMutableDictionary alloc]initWithDictionary:options]; NSLog(@"dictionary in init method %@",self.optionsDict); that NSLog logs the contents of the dictionary, and it looks like its working. then later when I do this: - (void)viewDidLoad { SDJConnection *connection = [[SDJConnection alloc]init]; self.dataArray = [connection getEventInfoWithURL:[dict objectForKey:@"urlkey"]]; NSLog(@"dictionary in connection contains: %@", [dict objectForKey:@"urlkey"]); [_tableView reloadData]; the dictionary returns null. Ive tried adjusting the property attributes, and it didn't work with either strong or retain. Any ideas?? THANKS!!

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• how do I get eclipse to use a different compiler version for Java?

  - by codeman73

  It seems like this should be a simple task, with the options in the Preferences menu for different JREs and the ability to set different compiler and build paths per project. However, it also seems to simply not work. For example, I have my JAVA_HOME set to a jre for Java 1.6. It's still not clear to me how Eclipse uses this, but it appears to be defaulting to this and not taking the project overrides. I have also installed Java 1.5, and added a JRE for this in eclipse in the Java-Installed JREs section. In my project, I've set the compiler compliance level to 1.5. In the build path for the project, I've added the System Library for the Java 1.5 JRE. However, I'm getting compile errors for a class that implements PreparedStatement for not implementing abstract methods that only exist in Java 1.6 PreparedStatement. Specifically, the methods setAsciiStream(int, InputStream, long) and setAsciiStream(int, InputStream) Strangely enough, it worked when we were compiling it against Java 1.4, which it was originally written for. We added the JREs for Java 1.4 and referenced that system library in the project, and set the project's compiler level to 1.4, and it works fine. But when I do the same changes to try to point to Java 1.5, it instead uses 1.6. Any ideas why?

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• Best practices for JQuery namespaces + general purpose utility functions

  - by Armchair Bronco

  What are some current "rules of thumb" for implementing JQuery namespaces to host general purpose utility functions? I have a number of JavaScript utility methods scattered in various files that I'd like to consolidate into one (or more) namespaces. What's the best way to do this? I'm currently looking at two different syntaxes, listed in order of preference: //****************************** // JQuery Namespace syntax #1 //****************************** if (typeof(MyNamespace) === "undefined") { MyNamespace = {}; } MyNamespace.SayHello = function () { alert("Hello from MyNamespace!"); } MyNamespace.AddEmUp = function (a, b) { return a + b; } //****************************** // JQuery Namespace syntax #2 //****************************** if (typeof (MyNamespace2) === "undefined") { MyNamespace2 = { SayHello: function () { alert("Hello from MyNamespace2!"); }, AddEmUp: function (a, b) { return a + b; } }; } Syntax #1 is more verbose but it seems like it would be easier to maintain down the road. I don't need to add commas between methods, and I can left align all my functions. Are there other, better ways to do this?

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• How to handle update events on a ASP.NET GridView?

  - by Bogdan M

  Hello, This may sound silly, but I need to find out how to handle an Update event from a GridView. First of all, I have a DataSet, where there is a typed DataTable with a typed TableAdapter, based on a "select all query", with auto-generated Insert, Update, and Delete methods. Then, in my aspx page, I have an ObjectDataSource related to my typed TableAdapter on Select, Insert, Update and Delete methods. Finnally, I have a GridView bound to this ObjectDataSource, with default Edit, Update and Cancel links. How should I implement the edit functionality? Should I have something like this? protected void GridView_RowEditing(object sender, GridViewEditEventArgs e) { using(MyTableAdapter ta = new MyTableAdapter()) { ta.Update(...); TypedDataTable dt = ta.GetRecords(); this.GridView.DataSource = dt; this.GridView.DataBind(); } } In this scenario, I have the feeling that I update some changes to the DB, then I retrive and bind all the data, and not only the modified parts. Is there any way to update only the DataSet, and this to update on his turn the DataBase and the GridView? I do not want to retrive all the data after a CRUD operations is performed, I just want to retrive the changes made. Thanks. PS: I'm using .NET 3.5 and VS 2008 with SP1.

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• C# ASP.NET Binding Controls via Generic Method

  - by OverTech

  I have a few web applications that I maintain and I find myself very often writing the same block of code over and over again to bind a GridView to a data source. I'm trying to create a Generic method to handle data binding but I'm having trouble getting it to work with Repeaters and DataLists. Here is the Generic method I have so far: public void BindControl<T>(T control, SqlCommand sql) where T : System.Web.UI.WebControls.BaseDataBoundControl { cmd = sql; cn.Open(); SqlDataReader dr = cmd.ExecuteReader(); if (dr.HasRows) { control.DataSource = dr; control.DataBind(); } dr.Close(); cn.Close(); } That way I can just define my CommandText then make a call to "BindControls(myGridView, cmd)" instead of retyping this same basic block of code every time I need to bind a grid. The problem is, this doesn't work with Repeaters or DataLists. Each of these controls inherit their respective "DataSource" and "DataBind" methods from different classes. Someone on another forum suggested that I implement an interface, but I'm not sure how to make that work either. The GridView, Datalist and Repeater get their respective "DataBind" methods from BaseDataBoundControl, BaseDataList, and Repeater classes. How would I go about creating a single interface to tie them all together? Or am I better off just using 3 overloads for this method? Dave

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• using compareTo in Binary Search Tree program

  - by Scott Rogener

  I've been working on this program for a few days now and I've implemented a few of the primary methods in my BinarySearchTree class such as insert and delete. Insert seemed to be working fine, but once I try to delete I kept getting errors. So after playing around with the code I wanted to test my compareTo methods. I created two new nodes and tried to compare them and I get this error: Exception in thread "main" java.lang.ClassCastException: TreeNode cannot be cast to java.lang.Integer at java.lang.Integer.compareTo(Unknown Source) at TreeNode.compareTo(TreeNode.java:16) at BinarySearchTree.myComparision(BinarySearchTree.java:177) at main.main(main.java:14) Here is my class for creating the nodes: public class TreeNode<T> implements Comparable { protected TreeNode<T> left, right; protected Object element; public TreeNode(Object obj) { element=obj; left=null; right=null; } public int compareTo(Object node) { return ((Comparable) this.element).compareTo(node); } } Am I doing the compareTo method all wrong? I would like to create trees that can handle integers and strings (seperatly of course)

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• How to perform a binary search on IList<T>?

  - by Daniel Brückner

  Simple question - given an IList<T> how do you perform a binary search without writing the method yourself and without copying the data to a type with build-in binary search support. My current status is the following. List<T>.BinarySearch() is not a member of IList<T> There is no equivalent of the ArrayList.Adapter() method for List<T> IList<T> does not inherit from IList, hence using ArrayList.Adapter() is not possible I tend to believe that is not possible with build-in methods, but I cannot believe that such a basic method is missing from the BCL/FCL. If it is not possible, who can give the shortest, fastest, smartest, or most beatiful binary search implementation for IList<T>? UPDATE We all know that a list must be sorted before using binary search, hence you can assume that it is. But I assume (but did not verify) it is the same problem with sort - how do you sort IList<T>? CONCLUSION There seems to be no build-in binary search for IList<T>. One can use First() and OrderBy() LINQ methods to search and sort, but it will likly have a performance hit. Implementing it yourself (as an extension method) seems the best you can do.

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• Intellisense on custom types in Iron Python

  - by Anish Patel

  Hi everybody, I'm just starting to play around with IronPython and am having a hard time using it with custom types created in C#. I can get IronPython to load in assemblies from C# classes, but I'm struggling without the help of intellisense. If I have a class in C# as defined below, how can I make it so that IronPython will be able to see the methods/properties that are available in it? public class Person { public string Name { get; set; } public int Age{ get; set; } public double Weight{ get; set; } public double Height { get; set; } public double CalculateBMI() { return Weight/Math.Pow(Height, 2); } } In Iron python I'd instance a Person object as follows: newPerson = Person() newPerson.Name = 'John' newPerson.Age = 25 newPerson.Weight = 75 newPerson.Height = 1.70 newPerson.CalculateBMI() The thing that is annoying me is that I want to be able to say newPerson = Person() And then be able to see all the methods and properties associated with the person object whenever I type: newPerson. Anyone have any ideas if this can be done?

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• Dual usage of asp.net mvc and php under same domain

  - by jim

  Hello all, I've got a scenario where we have a customer who has a linux hosted php app (joomla) that they wish to integrate with some back-end asp.net mvc functionality that was created for a 'sister' site. Basically, the mvc site has prices and stock availability methods which (in the sister site) populates dropdown lists and other 'order' style info on the pages. I've been tasked with looking at the integration options to allow the php site to use this info as a 'service'. (as ever, these guys are looking at cost of ownership, maintenence etc, so this is their preferred route) Has anyone done anything similar with success?? I'd imagine (much like the sister site) liberal doses of ajax will be employed in order to populate portions of the page on demand. So this may have a bearing on any suggestions that you may have. Also, the methods that are being called ultimately end up populating the same database, so there are no issues with correlating the ID's across the different platforms. I don't really want to go down any 'iframe' type route if at all possible, tho' reality may dictate this as being an option. I'm possibly (naively) imagining that i could simply invoke the mvc functions directly from the php app with some sort of 'session' variable being passed for authentication. pretty tall order or pretty straightfwd?? cheers jim

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• Returning true or error message in Ruby

  - by seaneshbaugh

  I'm wondering if writing functions like this is considered good or bad form. def test(x) if x == 1 return true else return "Error: x is not equal to one." end end And then to use it we do something like this: result = test(1) if result != true puts result end result = test(2) if result != true puts result end Which just displays the error message for the second call to test. I'm considering doing this because in a rails project I'm working on inside my controller code I make calls to a model's instance methods and if something goes wrong I want the model to return the error message to the controller and the controller takes that error message and puts it in the flash and redirects. Kinda like this def create @item = Item.new(params[:item]) if [email protected]? result = @item.save_image(params[:attachment][:file]) if result != true flash[:notice] = result redirect_to(new_item_url) and return end #and so on... That way I'm not constructing the error messages in the controller, merely passing them along, because I really don't want the controller to be concerned with what the save_image method itself does just whether or not it worked. It makes sense to me, but I'm curious as to whether or not this is considered a good or bad way of writing methods. Keep in mind I'm asking this in the most general sense pertaining mostly to ruby, it just happens that I'm doing this in a rails project, the actual logic of the controller really isn't my concern.

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• JUnit confusion: use 'extend Testcase' or '@Test' ?

  - by Rabarberski

  I've found the proper use (or at least the documentation) of JUnit very confusing. This question serves both as a future reference and as a real question. If I've understood correctly, there are two main approaches to create and run a JUnit test: Approach A: create a class that extends TestCase, and start test methods with the word test. When running the class as a JUnit Test (in Eclipse), all methods starting with the word test are automatically run. import junit.framework.TestCase; public class DummyTestA extends TestCase { public void testSum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Approach B: create a 'normal' class and prepend a @Test annotation to the method. Note that you do NOT have to start the method with the word test. import org.junit.*; import static org.junit.Assert.*; public class DummyTestB { @Test public void Sum() { int a = 5; int b = 10; int result = a + b; assertEquals(15, result); } } Mixing the two seems not to be a good idea, see e.g. this stackoverflow question: Now, my questions(s): What is the preferred approach, or when would you use one instead of the other? Approach B allows for testing for exceptions by extending the @Test annotation like in @Test(expected = ArithmeticException.class). But how do you test for exceptions when using approach A? When using approach A, you can group a number of test classes in a test suite. TestSuite suite = new TestSuite("All tests");<br/> suite.addTestSuite(DummyTestA.class); suite.addTestSuite(DummyTestAbis.class);` But this can't be used with approach B (since each testclass should subclass TestCase). What is the proper way to group tests for approach B?

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• general learning methodology

  - by momo

  just wanted to hear on the different general learning paths people embark on when learning a new language/framework. the one i currently use, which is how i learned bash and am currently learning python, is: instant hacking tutorial (very short tutorial introducing the basic syntax, variable declaration, loops, data types, etc. and how they are generally used) in depth tutorial with good programming style and slightly topic-specific (e.g. Mark Pilgrim's Dive into Python), important topics for me personally are regex methods, file IO, and ways the different data types are utilized best (i wrote a very primitive bayesian spam filter using python's dictionaries to keep track of word occurrences) spaced-repition of syntax or short recipes (i use anki, with questions like 'create dictionary with filename and filesize metadata, human-readable' or simpler ones like 'match 0 - 3 occurences of the letter M in a string', or 'return/create an iterator from two sequences') the use of spaced-repitition has been invaluable, and i credit it with the ease that i can recall/create python algorithms. however, i've recently started looking into django, and i've found that spaced-repitition, at least in my case, doesn't work very well for learning a framework, it works best with short code recipes (either that or i should start looking into more basic django framework tutorials). the problem i'm encountering is that since framework programming is not only algorithms, but actually learning the API, which can be quite complex since you have to learn all the methods, modules, the places where they are stored, and the sequence of which things have to be done. for ex. in django to start a project that deals with polls (from the django tutorial), one has to create the project, edit the settings.py file, create the polls app, edit the models.py file (which requires knowing the classes that are present in the module models), edit the urls.py file, etc. i found that my spaced-repition method didn't work very well for this type of learning, so i wanted to ask you guys what method(s) you use for learning the different frameworks/APIs.

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• Is there a safe / standard way to manage unstructured memory in C++?

  - by andand

  I'm building a toy VM that requires a block of memory for storing and accessing data elements of different types and of different sizes. I've done this by writing a wrapper class around a uint8_t[] data block of the needed size. That class has some template methods to write / read typed data elements to / from arbitrary locations in the memory block, both of which check to make certain the bounds aren't violated. These methods use memmove in what I hope is a more or less safe manner. That said, while I am willing to press on in this direction, I've got to believe that other with more expertise have been here before and might be willing to share their wisdom. In particular: 1) Is there a class in one of the C++ standards (past, present, future) that has been defined to perform a function similar to what I have outlined above? 2) If not, is there a (preferably free as in beer) library out there that does? 3) Short of that, besides bounds checking and the inevitable issue of writing one type to a memory location and reading a different from that location, are there other issues I should be aware of? Thanks.-&&

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• Refactor throwing not null exception if using a method that has a dependency on a certain contructor

  - by N00b

  In the method below the second constructor accepts a ForumThread object which the IncrementViewCount() method uses. There is a dependency between the method and that particular constructor. Without extracting into a new private method the null check in IncrementViewCount() and LockForumThread() (plus other methods not shown) is there some simpler re-factoring I can do or the implementation of a better design practice for this method to guard against the use of the wrong constructor with these dependent methods? Thank you for any suggestions in advance. private readonly IThread _forumLogic; private readonly ForumThread _ft; public ThreadLogic(IThread forumLogic) : this(forumLogic, null) { } public ThreadLogic(IThread forumLogic, ForumThread ft) { _forumLogic = forumLogic; _ft = ft; } public void Create(ForumThread ft) { _forumLogic.SaveThread(ft); } public void IncrementViewCount() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); lock (_ft) { _ft.ViewCount = _ft.ViewCount + 1; _forumLogic.SaveThread(_ft); } } public void LockForumThread() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); _ft.ThreadLocked = true; _forumLogic.SaveThread(_ft); }

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• UITouch Events and Table Views

  - by Andy

  I'm working on a navigation-based iPhone-only app that serves two main purposes: One, to present data in a hierarchical view, allowing users to drill down and eventually edit said data, and, two, to all users to perform a default action when the table view cell is tapped. I now need to offer a small set of options tied to the same data; however, both the didSelectRowAtIndexPath: and accessoryButtonTappedForRowAtIndexPath: methods are obviously taken. So, my options seem to be to implement a double-tap method, wherein the small list of additional options would be presented after (you guessed it) a double-tap on said table row; or, preferably, a tap-and-hold method. From what I can tell, tap-and-hold seems like the way to go in SDK 4.0 - which does me no good right this red-hot minute. I decided to go with the double-tap option, but I'm having a little trouble. First and foremost, the touchesBegan:withEvent: method does not seem to be getting called at all; a breakpoint placed within the method is never called while the application runs, and the table view responds exactly as it did before I inserted the method (which is to say, it performs the default action): - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *aTouch = [touches anyObject]; if (aTouch.tapCount == 2) { [NSObject cancelPreviousPerformRequestsWithTarget:self]; } } Second, I don't really need to handle a single-tap - the didSelectRowAtIndexPath: method can handle the single-tap just fine. The double-tap is the funky one I want to handle. I suspect the answer is going to contain the phrase, "You can't have the table view handle the single-tap and the touchesBegan: method handle the double-tap. The touch handling methods have to handle all of them." I would really appreciate some guidance from some of you who've dealt with this issue. Thanks in advance.

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• Different EF Property DataType than Storage Layer Possible?

  - by dj_kyron

  Hi, I am putting together a WCF Data Service for PatientEntities using Entity Framework. My solution needs to address these requirements: Property DateOfBirth of entity Patient is stored in SQL Server as string. It would be ideal if the entity class did not also use the "string" type but rather a DateTime type. (I would expect this to be possible since we're abstracting away from the storage layer). Where could a conversion mechanism be put in place that would convert to and from DateTime/string so that the entity and SQL Server are in sync?. I cannot change the storage layer's structure, so I have to work around it. WCF Data Services (Read-only, so no need for saving changes) need to be used since clients will be able to use LINQ expressions to consume the service. They can generate results based on any given query scenario they need and not be constrained by a single method such as GetPatient(int ID). I've tried to use DTOs, but run into problem of mapping the ObjectContext to a DTO, I don't think that is theoretically possible...or too complicated if it is. I've tried to use Self Tracking Entities but they require the metadata from the .edmx file if I'm correct, and this isn't allowing a different property data type. I also want to add customizations to my Entity getter methods so that a property "MRN" of type "string" needs to have .Replace("MR~", string.Empty) performed before it is returned. I can add this to the getter methods but the problem with that is Entity Framework will overwrite that next time it refreshes the entity classes. Is there a permanent place I can put these? Should I use POCO instead? How would that work with WCF Data Services? Where would the service grab the metadata?

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• Why does adding Crossover to my Genetic Algorithm give me worse results?

  - by MahlerFive

  I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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• OO vs Simplicity when it comes to user interaction

  - by Oetzi

  Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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• How to get a Class literal from a generically specific Class

  - by h2g2java

  There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

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• Importing data from third party datasource (open architecture design )

  - by mare

  How would you design an application (classes, interfaces in class library) in .NET when we have a fixed database design on our side and we need to support imports of data from third party data sources, which will most likely be in XML? For instance, let us say we have a Products table in our DB which has columns Id Title Description TaxLevel Price and on the other side we have for instance Products: ProductId ProdTitle Text BasicPrice Quantity. Currently I do it like this: Have the third party XML convert to classes and XSD's and then deserialize its contents into strong typed objects (what we get as a result of this process is classes like ThirdPartyProduct, ThirdPartyClassification, etc.). Then I have methods like this: InsertProduct(ThirdPartyProduct newproduct) I do not use interfaces at the moment but I would like them to. What I would like is implement something like public class Contoso_ProductSynchronization : ProductSynchronization InsertProduct(ContosoProduct p) where ProductSynchronization will be an interface or abstract class. There will most likely be many implementations of ProductSynchronization. I cannot hardcode the types - classes like ContosoProduct, NorthwindProduct might be created from the third party XML's (so preferably I would continue to use deserialization). Hopefully someone will understand what I'm trying to explain here. Just imagine you are the seller and you have numerous providers and each one uses their own proprietary XML format. I don't mind the development, which will of course be needed everytime new format appears, because it will only require 10-20 methods to be implemented, I just want the architecture to be open and support that.

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• c# delegate and abstract class

  - by BeraCim

  Hi all: I currently have 2 concrete methods in 2 abstract classes. One class contains the current method, while the other contains the legacy method. E.g. // Class #1 public abstract class ClassCurrent<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllRootNodes(int i) { //some code } } // Class #2 public abstract class MyClassLegacy<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllLeafNodes(int j) { //some code } } I want the corresponding method to run in their relative scenarios in the app. I'm planning to write a delegate to handle this. The idea is that I can just call the delegate and write logic in it to handle which method to call depending on which class/project it is called from (at least thats what I think delegates are for and how they are used). However, I have some questions on that topic (after some googling): 1) Is it possible to have a delegate that knows the 2 (or more) methods that reside in different classes? 2) Is it possible to make a delegate that spawns off abstract classes (like from the above code)? (My guess is a no, since delegates create concrete implementation of the passed-in classes) 3) I tried to write a delegate for the above code. But I'm being technically challenged: public delegate List GetAllNodesDelegate(int k); GetAllNodesDelegate del = new GetAllNodesDelegate(ClassCurrent.GetAllRootNodes); I got the following error: An object reference is required for the non-static field, method, property ClassCurrent<BaseNode>.GetAllRootNodes(int) I might have misunderstood something... but if I have to manually declare a delegate at the calling class, AND to pass in the function manually as above, then I'm starting to question whether delegate is a good way to handle my problem. Thanks.

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• Should java try blocks be scoped as tightly as possible?

  - by isme

  I've been told that there is some overhead in using the Java try-catch mechanism. So, while it is necessary to put methods that throw checked exception within a try block to handle the possible exception, it is good practice performance-wise to limit the size of the try block to contain only those operations that could throw exceptions. I'm not so sure that this is a sensible conclusion. Consider the two implementations below of a function that processes a specified text file. Even if it is true that the first one incurs some unnecessary overhead, I find it much easier to follow. It is less clear where exactly the exceptions come from just from looking at statements, but the comments clearly show which statements are responsible. The second one is much longer and complicated than the first. In particular, the nice line-reading idiom of the first has to be mangled to fit the readLine call into a try block. What is the best practice for handling exceptions in a funcion where multiple exceptions could be thrown in its definition? This one contains all the processing code within the try block: void processFile(File f) { try { // construction of FileReader can throw FileNotFoundException BufferedReader in = new BufferedReader(new FileReader(f)); // call of readLine can throw IOException String line; while ((line = in.readLine()) != null) { process(line); } } catch (FileNotFoundException ex) { handle(ex); } catch (IOException ex) { handle(ex); } } This one contains only the methods that throw exceptions within try blocks: void processFile(File f) { FileReader reader; try { reader = new FileReader(f); } catch (FileNotFoundException ex) { handle(ex); return; } BufferedReader in = new BufferedReader(reader); String line; while (true) { try { line = in.readLine(); } catch (IOException ex) { handle(ex); break; } if (line == null) { break; } process(line); } }

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• How do I create efficient instance variable mutators in Matlab?

  - by Trent B

  Previously, I implemented mutators as follows, however it ran spectacularly slowly on a recursive OO algorithm I'm working on, and I suspected it may have been because I was duplicating objects on every function call... is this correct? %% Example Only obj2 = tripleAllPoints(obj1) obj.pts = obj.pts * 3; obj2 = obj1 end I then tried implementing mutators without using the output object... however, it appears that in MATLAB i can't do this - the changes won't "stick" because of a scope issue? %% Example Only tripleAllPoints(obj1) obj1.pts = obj1.pts * 3; end For application purposes, an extremely simplified version of my code (which uses OO and recursion) is below. classdef myslice properties pts % array of pts nROW % number of rows nDIM % number of dimensions subs % sub-slices end % end properties methods function calcSubs(obj) obj.subs = cell(1,obj.nROW); for i=1:obj.nROW obj.subs{i} = myslice; obj.subs{i}.pts = obj.pts(1:i,2:end); end end function vol = calcVol(obj) if obj.nROW == 1 obj.volume = prod(obj.pts); else obj.volume = 0; calcSubs(obj); for i=1:obj.nROW obj.volume = obj.volume + calcVol(obj.subs{i}); end end end end % end methods end % end classdef

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• How can i get rid of 'ORA-01489: result of string concatenation is too long' in this query?

  - by core_pro

  this query gets the dominating sets in a network. so for example given a network A<----->B B<----->C B<----->D C<----->E D<----->C D<----->E F<----->E it returns B,E B,F A,E but it doesn't work for large data because i'm using string methods in my result. i have been trying to remove the string methods and return a view or something but to no avail With t as (select 'A' as per1, 'B' as per2 from dual union all select 'B','C' from dual union all select 'B','D' from dual union all select 'C','B' from dual union all select 'C','E' from dual union all select 'D','C' from dual union all select 'D','E' from dual union all select 'E','C' from dual union all select 'E','D' from dual union all select 'F','E' from dual) ,t2 as (select distinct least(per1, per2) as per1, greatest(per1, per2) as per2 from t union select distinct greatest(per1, per2) as per1, least(per1, per2) as per1 from t) ,t3 as (select per1, per2, row_number() over (partition by per1 order by per2) as rn from t2) ,people as (select per, row_number() over (order by per) rn from (select distinct per1 as per from t union select distinct per2 from t) ) ,comb as (select sys_connect_by_path(per,',')||',' as p from people connect by rn > prior rn ) ,find as (select p, per2, count(*) over (partition by p) as cnt from ( select distinct comb.p, t3.per2 from comb, t3 where instr(comb.p, ','||t3.per1||',') > 0 or instr(comb.p, ','||t3.per2||',') > 0 ) ) ,rnk as (select p, rank() over (order by length(p)) as rnk from find where cnt = (select count(*) from people) order by rnk ) select distinct trim(',' from p) as p from rnk where rnk.rnk = 1`

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