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• Should a Perl constructor return an undef or a "invalid" object?

  - by DVK

  Question: What is considered to be "Best practice" - and why - of handling errors in a constructor?. "Best Practice" can be a quote from Schwartz, or 50% of CPAN modules use it, etc...; but I'm happy with well reasoned opinion from anyone even if it explains why the common best practice is not really the best approach. As far as my own view of the topic (informed by software development in Perl for many years), I have seen three main approaches to error handling in a perl module (listed from best to worst in my opinion): Construct an object, set an invalid flag (usually "is_valid" method). Often coupled with setting error message via your class's error handling. Pros: Allows for standard (compared to other method calls) error handling as it allows to use $obj->errors() type calls after a bad constructor just like after any other method call. Allows for additional info to be passed (e.g. 1 error, warnings, etc...) Allows for lightweight "redo"/"fixme" functionality, In other words, if the object that is constructed is very heavy, with many complex attributes that are 100% always OK, and the only reason it is not valid is because someone entered an incorrect date, you can simply do "$obj->setDate()" instead of the overhead of re-executing entire constructor again. This pattern is not always needed, but can be enormously useful in the right design. Cons: None that I'm aware of. Return "undef". Cons: Can not achieve any of the Pros of the first solution (per-object error messages outside of global variables and lightweight "fixme" capability for heavy objects). Die inside the constructor. Outside of some very narrow edge cases, I personally consider this an awful choice for too many reasons to list on the margins of this question. UPDATE: Just to be clear, I consider the (otherwise very worthy and a great design) solution of having very simple constructor that can't fail at all and a heavy initializer method where all the error checking occurs to be merely a subset of either case #1 (if initializer sets error flags) or case #3 (if initializer dies) for the purposes of this question. Obviously, choosing such a design, you automatically reject option #2.

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• Defining jUnit Test cases Correctly

  - by Epitaph

  I am new to Unit Testing and therefore wanted to do some practical exercise to get familiar with the jUnit framework. I created a program that implements a String multiplier public String multiply(String number1, String number2) In order to test the multiplier method, I created a test suite consisting of the following test cases (with all the needed integer parsing, etc) @Test public class MultiplierTest { Multiplier multiplier = new Multiplier(); // Test for 2 positive integers assertEquals("Result", 5, multiplier.multiply("5", "1")); // Test for 1 positive integer and 0 assertEquals("Result", 0, multiplier.multiply("5", "0")); // Test for 1 positive and 1 negative integer assertEquals("Result", -1, multiplier.multiply("-1", "1")); // Test for 2 negative integers assertEquals("Result", 10, multiplier.multiply("-5", "-2")); // Test for 1 positive integer and 1 non number assertEquals("Result", , multiplier.multiply("x", "1")); // Test for 1 positive integer and 1 empty field assertEquals("Result", , multiplier.multiply("5", "")); // Test for 2 empty fields assertEquals("Result", , multiplier.multiply("", "")); In a similar fashion, I can create test cases involving boundary cases (considering numbers are int values) or even imaginary values. 1) But, what should be the expected value for the last 3 test cases above? (a special number indicating error?) 2) What additional test cases did I miss? 3) Is assertEquals() method enough for testing the multiplier method or do I need other methods like assertTrue(), assertFalse(), assertSame() etc 4) Is this the RIGHT way to go about developing test cases? How am I "exactly" benefiting from this exercise? 5)What should be the ideal way to test the multiplier method? I am pretty clueless here. If anyone can help answer these queries I'd greatly appreciate it. Thank you.

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• What is the best way to update an unattached entity on Entity Framework?

  - by Carlos Loth

  Hi, In my project I have some data classes to retrieve data from the database using the Entity Framework. We called these classes *EntityName*Manager. All of them have a method to retrieve entities from database and they behave most like this: static public EntityA SelectByName(String name) { using (var context = new ApplicationContext()) { var query = from a in context.EntityASet where a.Name == name select a; try { var entityA = query.First(); context.Detach(entityA); return entityA; } catch (InvalidOperationException ex) { throw new DataLayerException( String.Format("The entityA whose name is '{0}' was not found.", name), ex); } } } You can see that I detach the entity before return it to the method caller. So, my question is "what is the best way to create an update method on my *EntityA*Manager class?" I'd like to pass the modified entity as a parameter of the method. But I haven't figured out a way of doing it without going to the database and reload the entity and update its values inside a new context. Any ideas? Thanks in advance, Carlos Loth.

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• Function syntax puzzler in scalaz

  - by oxbow_lakes

  Following watching Nick Partidge's presentation on deriving scalaz, I got to looking at this example, which is just awesome: import scalaz._ import Scalaz._ def even(x: Int) : Validation[NonEmptyList[String], Int] = if (x % 2 ==0) x.success else "not even: %d".format(x).wrapNel.fail println( even(3) <|*|> even(5) ) //prints: Failure(NonEmptyList(not even: 3, not even: 5)) I was trying to understand what the <|*|> method was doing, here is the source code: def <|*|>[B](b: M[B])(implicit t: Functor[M], a: Apply[M]): M[(A, B)] = <**>(b, (_: A, _: B)) OK, that is fairly confusing (!) - but it references the <**> method, which is declared thus: def <**>[B, C](b: M[B], z: (A, B) => C)(implicit t: Functor[M], a: Apply[M]): M[C] = a(t.fmap(value, z.curried), b) So I have a few questions: How come the method appears to take a monad of one type parameter (M[B]) but can get passed a Validation (which has two type paremeters)? How does the syntax (_: A, _: B) define the function (A, B) => C which the 2nd method expects? It doesn't even define an output via =>

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• Wizard form in Struts

  - by Kuntal Basu

  I am creating a wizard in Struts. It cotains 4 steps. For Each step I have separate ActionClass say:- Step1Action.java Step2Action.java Step3Action.java Step4Action.java and in each class there are 2 methods input() and process(). input() method is for showing the page in input mode process() method is will be use for processing the submitted data (if validation is ok) I am carrying all data upto the last step in a session. And saving all of them in database in the last step Similaly 4 action tags in struts.xml like :- <action name="step1" class="com.mycomp.myapp.action.Step1Action1" method="input"> <result name="success" type="redirectAction">step2</result> <result name="input">/view/step1.jsp</result> </action> <action name="step2" class="com.mycomp.myapp.action.Step1Action2" method="input"> <result name="success" type="redirectAction">step3</result> <result name="input">/view/step2.jsp</result> </action> But I think I am going wrong. Please Tell me How will I handle This case?

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• python: how to design a container with elements that must reference their container

  - by Luke404

  (the title is admittedly not that great. Please forgive my English, this is the best I could think of) I'm writing a python script that will manage email domains and their accounts, and I'm also a newby at OOP design. My two (related?) issues are: the Domain class must do special work to add and remove accounts, like adding/removing them to the underlying implementation how to manage operations on accounts that must go through their container To solve the former issue I'd add a factory method to the Domain class that'll build an Account instance in that domain, and a 'remove' (anti-factory?) method to handle deletions. For the latter this seems to me "anti-oop" since what would logically be an operation on an Account (eg, change password) must always reference the containing Domain. Seems to me that I must add to the Account a reference back to the Domain and use that to get data (like the domain name) or call methods on the Domain class. Code example (element uses data from the container) that manages an underlying Vpopmail system: class Account: def __init__(self, name, password, domain): self.name = name self.password = password self.domain = domain def set_password(self, password): os.system('vpasswd %s@%s %s' % (self.name, self.domain.name, password) self.password = password class Domain: def __init__(self, domain_name): self.name = domain_name self.accounts = {} def create_account(self, name, password): os.system('vadduser %s@%s %s' % (name, self.name, password)) account = Account(name, password, self) self.accounts[name] = account def delete_account(self, name): os.system('vdeluser %s@%s' % (name, self.name)) del self.accounts[name] another option would be for Account.set_password to call a Domain method that would do the actual work - sounds equally ugly to me. Also note the duplication of data (account name also as dict key), it sounds logical (account names are "primary key" inside a domain) but accounts need to know their own name.

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• Replacing/Extending Visual Studio's Generate Stub in Visual Studio 2010

  - by devoured elysium

  When we write the name of a method that doesn't exist, Visual Studio 2010 asks us if we'd like to generate a method stub with that name. What I'd like to know if is it possible to replace that same code stub generating command with one made by myself. I never did any kind of extensibility programming for Visual Studio so I have a couple of questions: How hard is it? Is it something I can learn in a couple of nights, or is it something that'll make me "lose" a lot of time? It seems to me that there isn't a lot of support for that kind of programming, as generally people are not that interested in developing solutions that extend the Visual Studio IDE. I searched on SO and it doesn't appear to have many threads about extending Visual Studio. I don't know how the generate method stub thing works in Visual Studio, but I just wanted to turn it into something a bit more flexible and useful. Has anyone dealt with these kind of things before, that can give me a pointer to where to start? I know of MS VSX site but that has a lot of resources and can be overwhelming for someone new to the subject as I am. What technology will I need to use? T4? Maybe I'll need to know a lot about the code, like Visual Studio does, so I can know other method's type arguments, names, etc. Is that what T4 is for? Thanks

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• SQLite assembly not copied to output folder for unit testing

  - by Groo

  Problem: SQLite assembly referenced in my DAL assembly does not get copied to the output folder when doing unit tests (Copy local is set to true). I am working on a .Net 3.5 app in VS2008, with NHibernate & SQLite in my DAL. Data access is exposed through the IRepository interface (repository factory) to other layers, so there is no need to reference NHibernate or the System.Data.SQLite assemblies in other layers. For unit testing, there is a public factory method (also in my DAL) which creates an in-memory SQLite session and creates a new IRepository implementation. This is also done to avoid have a shared SQLite in-memory config for all assemblies which need it, and to avoid referencing those DAL internal assemblies. The problem is when I run unit tests which reside a separate project - if I don't add System.Data.SQLite as a reference to the unit test project, it doesn't get copied to the TestResults...\Out folder (although this project references my DAL project, which references System.Data.SQLite, which has its Copy local property set to true), so the tests fail while NHibernate is being configured. If I add the reference to my testing project, then it does get copied and unit tests work. What am I doing wrong?

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• (C#) Get index of current foreach iteration

  - by Graphain

  Hi, Is there some rare language construct I haven't encountered (like the few I've learned recently, some on Stack Overflow) in C# to get a value representing the current iteration of a foreach loop? For instance, I currently do something like this depending on the circumstances: int i=0; foreach (Object o in collection) { ... i++; } Answers: @bryansh: I am setting the class of an element in a view page based on the position in the list. I guess I could add a method that gets the CSSClass for the Objects I am iterating through but that almost feels like a violation of the interface of that class. @Brad Wilson: I really like that - I've often thought about something like that when using the ternary operator but never really given it enough thought. As a bit of food for thought it would be nice if you could do something similar to somehow add (generically to all IEnumerable objects) a handle on the enumerator to increment the value that an extension method returns i.e. inject a method into the IEnumerable interface that returns an iterationindex. Of course this would be blatant hacks and witchcraft... Cool though... @crucible: Awesome I totally forgot to check the LINQ methods. Hmm appears to be a terrible library implementation though. I don't see why people are downvoting you though. You'd expect the method to either use some sort of HashTable of indices or even another SQL call, not an O(N) iteration... (@Jonathan Holland yes you are right, expecting SQL was wrong) @Joseph Daigle: The difficulty is that I assume the foreach casting/retrieval is optimised more than my own code would be. @Jonathan Holland: Ah, cheers for explaining how it works and ha at firing someone for using it.

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• How to avoid "Illegal type in constant pool" using "ldc_w <classname>" in Jasmin?

  - by jazzdev

  I'm writing a compiler that generates Jasmin code and want to invoke a method that takes a Class as a parameter. public class CTest { public static void main(String[] args) throws Exception { java.lang.reflect.Array.newInstance(CTest.class, 0); } } So in Jasmin, I think that should be: .class public CTest2 .super java/lang/Object .method public static main([Ljava/lang/String;)V .limit stack 2 .limit locals 1 ldc_w CTest2 iconst_0 invokestatic java/lang/reflect/Array/newInstance(Ljava/lang/Class;I)Ljava/lang/Object; pop return .end method When I assemble it and run it I get: Exception in thread "main" java.lang.VerifyError: (class: CTest2, method: main signature: ([Ljava/lang/String;)V) Illegal type in constant pool Looking at the disassembled code for both CTest.class (the Java version) and CTest2.class (the Jasmin version) with "javap -c -verbose" they both appear to set up the constant pool the same way: const #2 = class #16; // CTest const #16 = Asciz CTest; 0: ldc_w #2; //class CTest const #14 = Asciz CTest2; const #17 = class #14; // CTest2 0: ldc_w #17; //class CTest2 I've fixed two bugs in Jasmin already, but I can't see what it's doing wrong when putting the class in the constant pool for "ldc_w" it puts classes in the constant pool for other instructions, like "new" and "anewarray" correctly. I've tried looking at the .class files with TraceClassVisitor in ASM, but it doesn't dump the constant pool. Any ideas what I can try next?

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• Problem with Spring @Configuration class

  - by easyrider

  Hi, i use class with @Configuration annotation to configure my spring application: @Configuration public class SpringConfiguration { @Value("${driver}") String driver; @Value("${url}") String url; @Value("${minIdle}") private int minIdle; // snipp .. @Bean(destroyMethod = "close") public DataSource dataSource() { DataSource dataSource = new DataSource(); dataSource.setDriverClassName(driver); dataSource.setUrl(url); dataSource.setUsername(user); dataSource.setPassword(password); dataSource.setMinIdle(minIdle); return dataSource; } and properties file in CLASSPATH driver=org.postgresql.Driver url=jdbc:postgresql:servicerepodb minIdle=1 I would like to get my DataSource configured object in my DAO class: ApplicationContext ctx = new AnnotationConfigApplicationContext(SpringConfiguration.class); DataSource dataSource = ctx.getBean(DataSource.class); But i get the error: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'springConfiguration': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private int de.hska.repo.configuration.SpringConfiguration.minIdle; nested exception is org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'int'; nested exception is **java.lang.NumberFormatException: For input string: "${minIdle}"** Caused by: java.lang.NumberFormatException: For input string: **"${minIdle}"** at java.lang.NumberFormatException.forInputString(**Unknown Source**) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.valueOf(Unknown Source) It worked with String properties (driver, url), but ${minIdle} (of type int) can't be resolved! Please help. Thanx in advance!

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• Is there added overhead to looking up a column in a DataTable by name rather than by index?

  - by Ben McCormack

  In a DataTable object, is there added overhead to looking up a column value by name thisRow("ColumnA") rather than by the column index thisRow(0)? In which scenarios might this be an issue. I work on a team that has lots of experience writing VB6 code and I noticed that didn't do column lookups by name for DataTable objects or data grids. Even in .NET code, we use a set of integer constants to reference column names in these types of objects. I asked our team lead why this was so, and he mentioned that in VB6, there was a lot of overhead in looking up data by column name rather than by index. Is this still true for .NET? Example code (in VB.NET, but same applies to C#): Public Sub TestADOData() Dim dt As New DataTable 'Set up the columns in the DataTable ' dt.Columns.Add(New DataColumn("ID", GetType(Integer))) dt.Columns.Add(New DataColumn("Name", GetType(String))) dt.Columns.Add(New DataColumn("Description", GetType(String))) 'Add some data to the data table ' dt.Rows.Add(1, "Fred", "Pitcher") dt.Rows.Add(3, "Hank", "Center Field") 'Method 1: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine( _ "{0,-2} {1,-10} {2,-30}", r("ID"), r("Name"), r("Description")) Next Console.WriteLine() 'Method 2: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine("{0,-2} {1,-10} {2,-30}", r(0), r(1), r(2)) Next End Sub Is there an case where method 2 provides a performance advantage over method 1?

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• iPhone SDK background thread image loading problem

  - by retailevolved

  I have created a grid view that displays six "cells" of content. In each cell, an image is loaded from the web. There are a multiple pages of this grid (the user moves through them by swiping up / down to see the next set of cells). Each cell has its own view controller. When these view controllers load, they use an ImageLoader class that I made to load and display an image. These view controllers implement an ImageLoaderDelegate that has a single method that gets called when the image is finished loading. ImageLoader does its work on a background thread and then simply notifies its delegate when it is done loading, passing the image to the delegate method. Trouble is that if the user moves on to the next page of grid content before the image has finished loading (releasing the GridCellViewControllers that use the ImageLoaders), the app crashes. I suspect that this is because along the line, an asynchronous method finishes and attempts to notify its delegate but can't because it's been released. Here's some code to give a better picture: GridCellViewController.m: - (void)viewDidLoad { [super viewDidLoad]; // ImageLoader _loader = [[ProductImageLoader alloc] init]; _loader.delegate = self; if(_boundObject) [_loader loadImageForProduct:_boundObject]; } //ImageLoaderDelegate method - (void) imageDidFinishLoading: (UIImage *)image { [_imgController setImage:image]; } ProductImageLoader.m - (void) loadImageForProduct: (Product *) product { // Get image on another thread [NSThread detachNewThreadSelector:@selector(getImageForProductInBackground:) toTarget:self withObject:product]; } - (void) getImageForProductInBackground: (Product *) product { NSAutoreleasePool *tempPool = [[NSAutoreleasePool alloc] init]; HttpRequestLoader *tempLoader = [[HttpRequestLoader alloc] init]; NSURL *tempUrl = [product getImageUrl]; NSData *imageData = tempUrl ? [tempLoader loadSynchronousDataFromAddress:[tempUrl absoluteString]] : nil; UIImage *image = [[UIImage alloc] initWithData:imageData]; [tempPool release]; if(delegate) [delegate imageDidFinishLoading:image]; } The app crashes with EXC_BAD_ACCESS. Disclaimer: The code has been slightly modified to focus on the issue at hand.

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• C# Taking a element off each time (stack)

  - by Sef

  Greetings, Have a question considering a program that stimulates a stack.(not using any build in stack features or any such) stack2= 1 2 3 4 5 //single dimension array of 5 elements By calling up a method "pop" the stack should look like the following: Basically taking a element off each time the stack is being "called" up again. stack2= 1 2 3 4 0 stack2= 1 2 3 0 0 stack2= 1 2 0 0 0 stack2= 1 0 0 0 0 stack2= 0 0 0 0 0 - for (int i = 1; i <= 6; i++) { number= TryPop(s2); //use number ShowStack(s2, "s2"); } Basically I already have code that fills my array with values (trough a push method). The pop method should basically take the last value and place it on 0. Then calls up the next stack and place the following on 0 (like shown above in stack2). The current pop method that keeps track of the top index (0 elements = 0 top, 1 element = 1 top etc..). Already includes a underflow warning if this goes on 0 or below (which is correct). public int Pop() { if(top <= 0) { throw new Exception("Stack underflow..."); } else { for (int j = tabel.Length - 1; j >= 0; j--) { //...Really not sure what to do here. } } return number; }/*Pop*/ Since in the other class I already have a loop (for loop shown above) that simulates 6 times the s2 stack. (first stack: 1 2 3 4 0, second stack 1 2 3 0 0 and so on.) How exactly do I take a element off each time? Either I have the entire display on 0 or the 0 in the wrong places / out of index errors. Thanks in advance!

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• Best practice when using WebMethods and session

  - by Abdel Olakara

  Hi all, I want to reduce postback in one of my application page and use ajax instead. I used the WebMethod to do so.. I have a static WebMethod that needs to access the session variables and modify. and on the client side, i am calling this method using jQuery. I tried accessing the session as follows: [WebMethod] public static void TestWebMethod() { if (HttpContext.Current.Session["pitems"] != null) { log.Debug("Using the existing list"); Product prod = (Product)HttpContext.Current.Session["pitems"]; List<Configs> confs = cart.GetConfigs(); foreach (Configs citem in confis) { log.Info(citem.Description); } } log.Info("Inside the method!"); } The values are displayed correctly and seems to work.. but i would like to know if this practice is allowed as the method is a static methods and would like to know how it will behave if multiple people access the application. I would also like to know how developers do these kind of tasks in ASP if this is not the right method. Thanks in advance for your suggestions and ideas, Abdel Olakara

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• Create an anonymous type object from an arbitrary text file

  - by Robert Harvey

  I need a sensible way to draw arbitrary text files into a C# program, and produce an arbitrary anonymous type object, or perhaps a composite dictionary of some sort. I have a representative text file that looks like this: adapter 1: LPe11002 Factory IEEE: 10000000 C97A83FC Non-Volatile WWPN: 10000000 C93D6A8A , WWNN: 20000000 C93D6A8A adapter 2: LPe11002 Factory IEEE: 10000000 C97A83FD Non-Volatile WWPN: 10000000 C93D6A8B , WWNN: 20000000 C93D6A8B Is there a way to get this information into an anonymous type object or some similar structure? The final anonymous type might look something like this, if it were composed in C# by hand: new { adapter1 = new { FactoryIEEE = "10000000 C97A83FC", Non-VolatileWWPN = "10000000 C93D6A8A", WWNN = "20000000 C93D6A8A" } adapter2 = new { FactoryIEEE = "10000000 C97A83FD", Non-VolatileWWPN = "10000000 C93D6A8B", WWNN = "20000000 C93D6A8B" } } Note that, as the text file's content is arbitrary (i.e. the keys could be anything), a specialized solution (e.g. that looks for names like "FactoryIEEE") won't work. However, the structure of the file will always be the same (i.e. indentation for groups, colons and commas as delimiters, etc). Or maybe I'm going about this the wrong way, and you have a better idea?

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• Problem with dropdownbox length

  - by vikitor

  Hello, I'm creating a javascript method that populates lists depending on a radio button selected previously. As it depends on animals or plants to populate it, my problem comes when I have to populate it after it's already been populated. I mean, the plants dropdownlist has 88 elements, and the animals is 888, when I try to come back from animals to plants, I get some of the animals. I know that my controller method is working properly because it returns the values I select, so the problem is the javascript method. Here is the code: if(selector == "sOrder") alert(document.getElementById(selector).options.length); for (i = 0; i < document.getElementById(selector).options.length; i++) { document.getElementById(selector).remove(i); } if (selector == "sOrder") alert(document.getElementById(selector).options.length); document.getElementById(selector).options[0] = new Option("-select-", "0", true, true); for (i = 1; i <= data.length; i++) { document.getElementById(selector).options[i] = new Option(data[i - 1].taxName, data[i - 1].taxRecID);} Here is the strange thing, when I enter the method I try to erase all the elements of the dropdownlist in order to populate it afterwards. As sOrder is the same selector I had previously selected, I get the elements, the thing is that the first alert I get the proper result, 888, but in the second alert, I should get a 0 right? It shows 444, so when I populate it again it just overrides the first 88 plants and then animals till 444. What am I doing wrong? Thank you all in advance, Victor

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• Rebinding and singleton-behaviour [NInject]

  - by Maximilian Csuk

  Hi! I have set up a NInject (using version 1.5) binding like this: Bind<ISessionFactory>().ToMethod<ISessionFactory>(ctx => { try { // create session factory, might fail because of database issues like wrong connection string } catch (Exception e) { throw new DatabaseException(e); } }).Using<SingletonBehavior>(); As you can see, this binding uses a singleton behavior but can also throw exception when something is not configured correctly, like a wrong connection string to the database. Now, when the creation of a session factory fails at first (throwing a database exception), NInject doesn't try to create the object again but always returns null. I would need NInject to check for null first and recreate when the instance is null, but of course not when there already is an instance successfully constructed (keeping it singleton). Like this: var a = Kernel.Get<ISessionFactory>(); // might fail, a = null // ... change some database settings var b = Kernel.Get<ISessionFactory>(); // might not fail anymore, b = ISessionFactory object Would I need to write a custom behavior or am I missing something else? Thanks for your answers!

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• Finding text orientation in image (angle for rotation)

  - by maximus

  There is an image captured by camera, and I need to find the angle of the text in order to rotate it to make the image better for OCR results. So I know that the fourier transform can be used for that purpose, My question is, does it really gives good results or may be it is better to use something different than that? Can you tell me if there is a good method for this purpose? I am afraid that not every image containing the text will give me a good result after using fourier transform method. Actually, if I make like it is written here: link text (see the part related with an example of text image) calculating the logarithm of the magnitude of the Fourier transform of image with text and then thresholding it, I get that points and I can calculate the line approximately passing through them, and after getting the line calculate the angle, and then make an affine transform, But, what if I do not get a good result every time using this method , and make a false transform? Any ideas please to judge wether the result is correct or not, or may be another method is better? The binary image can contain noise, even if there are not so much of them, the angle found as a result can be not accurate.

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• How can UISearchDisplayController autorelease cause crash in a different view controller?

  - by Tofrizer

  Hi, I have two view controllers A and B. From A, I navigate to view controller B as follows: // in View Controller A // navigateToB method -(void) navigateToB { BViewController *bViewController = [[BViewController alloc] initWithNibName: @"BView" bundle:nil]; bViewController.bProperty1 = SOME_STRING_CONSTANT; bViewController.title = @"A TITLE OF A VC's CHOOSING"; [self.navigationController pushViewController: bViewController animated:YES]; [bViewController release]; //<----- releasing 0x406c1e0 } In BViewController, the property bPropery1 is defined with copy as below (note, B also contains UITableView and other properties): @property (nonatomic, copy) NSString *bProperty1; Everything appeared to work fine when navigating back and forth between A and B. That is until I added a UISearchDisplayController to the table view contained in BViewController. Now when I navigate out of B, back to A, the app crashes. Stack trace shows what looks the search display controller being autoreleased at time of crash: #0 0x009663a7 in ___forwarding___ #1 0x009426c2 in __forwarding_prep_0___ #2 0x018c8539 in -[UISearchDisplayController _destroyManagedTableView] #3 0x018c8ea4 in -[UISearchDisplayController dealloc] #4 0x00285ce5 in NSPopAutoreleasePool NSZombies shows: -[BViewController respondsToSelector:]: message sent to deallocated instance 0x406c1e0 And malloc history on this points to the bViewController already released in A's navigateToB method above: Call [2] [arg=132]: thread_a065e720 |start ... <snip> ..._sendActionsForEvents:withEvent:] | -[UIControl sendAction:to:forEvent:] | - [UIApplication sendAction:to:from:forEvent:] | -[**AViewController navigateToB**] | +[NSObject alloc] | +[NSObject allocWithZone:] | _internal_class_createInstance | _internal_class_createInstanceFromZone | calloc | malloc_zone_calloc Can someone please give me any ideas on what is happening here? In navigateToB method, once the bViewController is released (after pushViewController), that's should be it for bViewController. Nothing else even knows about it as it is local to the navigateToB method block and it has been released. When navigating from B back to A, nothing is invoked in viewDidLoad, viewWillAppear etc that will re-enter navigateToB. It looks like somehow search display controller has a reference to something in my AViewController and so as it is autoreleased it is taking this "something" down with it but I cannot understand how this is possible, especially as I'm using copy to pass data between A and B. I'm going potty over this. I'm sure this is my mistake somewhere and so I turn to you, Stack Overflow legends for any words of wisdom or advice on how to resolve this. Many Thanks.

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• Duck type testing with C# 4 for dynamic objects.

  - by Tracker1

  I'm wanting to have a simple duck typing example in C# using dynamic objects. It would seem to me, that a dynamic object should have HasValue/HasProperty/HasMethod methods with a single string parameter for the name of the value, property, or method you are looking for before trying to run against it. I'm trying to avoid try/catch blocks, and deeper reflection if possible. It just seems to be a common practice for duck typing in dynamic languages (JS, Ruby, Python etc.) that is to test for a property/method before trying to use it, then falling back to a default, or throwing a controlled exception. The example below is basically what I want to accomplish. If the methods described above don't exist, does anyone have premade extension methods for dynamic that will do this? Example: In JavaScript I can test for a method on an object fairly easily. //JavaScript function quack(duck) { if (duck && typeof duck.quack === "function") { return duck.quack(); } return null; //nothing to return, not a duck } How would I do the same in C#? //C# 4 dynamic Quack(dynamic duck) { //how do I test that the duck is not null, //and has a quack method? //if it doesn't quack, return null }

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• Android change context for findViewById to super from inline class

  - by wuntee

  I am trying to get the value of a EditText in a dialog box. A the "*"'ed line in the following code, the safeNameEditText is null; i am assuming because the 'findVeiwById' is searching on the context of the 'AlertDialog.OnClickListener'; How can I get/change the context of that 'findViewById' call? protected Dialog onCreateDialog(int id) { AlertDialog.Builder builder = new AlertDialog.Builder(this); switch(id){ case DIALOG_NEW_SAFE: builder.setTitle(R.string.news_safe); builder.setIcon(android.R.drawable.ic_menu_add); LayoutInflater factory = LayoutInflater.from(this); View newSafeView = factory.inflate(R.layout.newsafe, null); builder.setView(newSafeView); builder.setPositiveButton(R.string.ok, new AlertDialog.OnClickListener(){ public void onClick(DialogInterface dialog, int which) { * EditText safeNameEditText = (EditText) findViewById(R.id.new_safe_name); String safeName = safeNameEditText.getText().toString(); Log.i(LOG, safeName); setSafeDao(safeName); } }); builder.setNegativeButton(R.string.cancel, new AlertDialog.OnClickListener(){ public void onClick(DialogInterface dialog, int which) { dialog.dismiss(); } }); return(builder.create()); default: return(null); } }

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• Help with Exception Handling in ASP.NET C# Application

  - by Shrewd Demon

  hi, yesterday i posted a question regarding the Exception Handling technique, but i did'nt quite get a precise answer, partly because my question must not have been precise. So i will ask it more precisely. There is a method in my BLL for authenticating user. If a user is authenticated it returns me the instance of the User class which i store in the session object for further references. the method looks something like this... public static UsersEnt LoadUserInfo(string email) { SqlDataReader reader = null; UsersEnt user = null; using (ConnectionManager cm = new ConnectionManager()) { SqlParameter[] parameters = new SqlParameter[1]; parameters[0] = new SqlParameter("@Email", email); try { reader = SQLHelper.ExecuteReader(cm.Connection, "sp_LoadUserInfo", parameters); } catch (SqlException ex) { //this gives me a error object } if (reader.Read()) user = new UsersDF(reader); } return user; } now my problem is suppose if the SP does not exist, then it will throw me an error or any other SQLException for that matter. Since this method is being called from my aspx.cs page i want to return some meaning full message as to what could have gone wrong so that the user understands that there was some problem and that he/she should retry logging-in again. but i can't because the method returns an instance of the User class, so how can i return a message instead ?? i hope i made it clear ! thank you.

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• Get current timepoint from Totem application

  - by ??O?????

  I want to find the exact time where a media file is currently paused at (or playing) in a running Totem instance using D-Bus. To be precise, what I want is available from the Totem python console (if the plugin exists and is enabled) by the following command: >>> print totem_object.props.current_time 732616 which I understand is milliseconds. So far: I've never used D-Bus before, so I'm in the process of going through D-Bus and python-dbus documentation. I've also fired up D-Feet and found that the org.gnome.Totem bus name and the /Factory object I can use the org.freedesktop.DBus.Properties interface methods. I'm currently at this point: >>> import dbus >>> seb= dbus.SessionBus() >>> t= seb.get_object('org.gnome.Totem', '/Factory') >>> tif= dbus.Interface(t, 'org.freedesktop.DBus.Properties') >>> tif.GetAll('') dbus.Dictionary({}, signature=dbus.Signature('sv')) I can't find even a proper how-to, so any help will be greatly appreciated.

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• TDD test data loading methods

  - by Dave Hanson

  I am a TDD newb and I would like to figure out how to test the following code. I am trying to write my tests first, but I am having trouble for creating a test that touches my DataAccessor. I can't figure out how to fake it. I've done the extend the shipment class and override the Load() method; to continue testing the object. I feel as though I end up unit testing my Mock objects/stubs and not my real objects. I thought in TDD the unit tests were supposed to hit ALL of the methods on the object; however I can never seem to test that Load() code only the overriden Mock Load My tests were write an object that contains a list of orders based off of shipment number. I have an object that loads itself from the database. public class Shipment { //member variables protected List<string> _listOfOrders = new List<string>(); protected string _id = "" //public properties public List<string> ListOrders { get{ return _listOfOrders; } } public Shipment(string id) { _id = id; Load(); } //PROBLEM METHOD // whenever I write code that needs this Shipment object, this method tries // to hit the DB and fubars my tests // the only way to get around is to have all my tests run on a fake Shipment object. protected void Load() { _listOfOrders = DataAccessor.GetOrders(_id); } } I create my fake shipment class to test the rest of the classes methods .I can't ever test the Real load method without having an actual DB connection public class FakeShipment : Shipment { protected new void Load() { _listOfOrders = new List<string>(); } } Any thoughts? Please advise. Dave

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