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• how can I implement Comparable more than once?

  - by codeman73

  I'm upgrading some code to Java 5 and am clearly not understanding something with Generics. I have other classes which implement Comparable once, which I've been able to implement. But now I've got a class which, due to inheritance, ends up trying to implement Comparable for 2 types. Here's my situation: I've got the following classes/interfaces: interface Foo extends Comparable<Foo> interface Bar extends Comparable<Bar> abstract class BarDescription implements Bar class FooBar extends BarDescription implements Foo With this, I get the error 'interface Comparable cannot be implemented more than once with different arguments...' Why can't I have a compareTo(Foo foo) implemented in FooBar, and also a compareTo(Bar) implemented in BarDescription? Isn't this simply method overloading?

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• Self host WCF (Windows Communication Foundation) Ajax services

  - by Wayne Lo

  I am having trouble to understand how to expose the WCF services through Javascript. Here are what I found after days of research: Exposing WCF services through Javascript but not self host: http://msdn.microsoft.com/en-us/library/bb472488.aspx In this example, it requires the creation of a .svc file <%@ServiceHost language="c#" Debug="true" Service="Microsoft.Samples.XmlAjaxService.CalculatorService" Factory="System.ServiceModel.Activation.WebServiceHostFactory" %> Self host WCF Ajax services but not exposing the services through Javascript. http://msdn.microsoft.com/en-us/library/bb943471%28v=VS.100%29.aspx Please help. Thanks.

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• Why is the base() constructor not necessary?

  - by Earlz

  Hello, I have a class structure like abstract class Animal { public Animal(){ //init stuff.. } } class Cat : Animal { public Cat(bool is_keyboard) : base() //NOTE here { //other init stuff } } Now then, look at the noted line. If you remove : base() then it will compile without an error. Why is this? Is there a way to disable this behavior? I have had multiple bugs now from forgetting the base() which I would have thought to be required on such a special thing as a constructor.

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• Huge amount of time sending data with suds and proxy

  - by Roman

  Hi everyone, I have the following code to send data through a proxy using suds: import suds t = suds.transport.http.HttpTransport() proxy = urllib2.ProxyHandler({'http': 'http://192.168.3.217:3128'}) opener = urllib2.build_opener(proxy) t.urlopener = opener ws = suds.client.Client('http://xxxxxxx/web.asmx?WSDL', transport=t) req = ws.factory.create('ActionRequest.request') req.SerialNumber = 'asdf' req.HostName = 'hola' res = ws.service.ActionRequest(req) I don't know why, but it can be sending data above 2 or 3 minutes, or even more and it raises a "Gateway timeout" exception sometimes. If I don't use the proxy, the amount of time used is above 2 seconds or less. Here is the SOAP reply: (ActionResponse){ Id = None Action = "Action.None" Objects = "" } The proxy is running right with other requests through urllib2, or using normal web browsers like firefox. Does anyone have any idea what's happening here with suds? Thanks a lot in advance!!!

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• How to handle JPA annotations for a pointer to a generic interface

  - by HDave

  I have a generic class that is also a mapped super class that has a private field that holds a pointer to another object of the same type: @MappedSuperclass public abstract class MyClass<T extends MyIfc<T>> implements MyIfc<T> { @OneToOne() @JoinColumn(name = "previous", nullable = true) private T previous; ... } My problem is that Eclipse is showing an error in the file at the OneToOne "Target Entity "T" for previous is not an Entity." All of the implementations of MyIfc are, in fact, Entities. I should also add that each concrete implementation that inherit from MyClass uses a different value for T (because T is itself) so I can't use the "targetEntity" attribute. I guess if there is no answer then I'll have to move this JPA annotation to all the concrete subclasses of MyClass. It just seems like JPA/Hibernate should be smart enough to know it'll all work out at run-time. Makes me wonder if I should just ignore this error somehow.

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• Is testability alone justification for dependency injection?

  - by fearofawhackplanet

  The advantages of DI, as far as I am aware, are: Reduced Dependencies More Reusable Code More Testable Code More Readable Code Say I have a repository, OrderRepository, which acts as a repository for an Order object generated through a Linq to Sql dbml. I can't make my orders repository generic as it performs mapping between the Linq Order entity and my own Order POCO domain class. Since the OrderRepository by necessity is dependent on a specific Linq to Sql DataContext, parameter passing of the DataContext can't really be said to make the code reuseable or reduce dependencies in any meaningful way. It also makes the code harder to read, as to instantiate the repository I now need to write new OrdersRepository(new MyLinqDataContext()) which additionally is contrary to the main purpose of the repository, that being to abstract/hide the existence of the DataContext from consuming code. So in general I think this would be a pretty horrible design, but it would give the benefit of facilitating unit testing. Is this enough justification? Or is there a third way? I'd be very interested in hearing opinions.

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• Rails - building an absolute url in a model's virtual attribute without url helper

  - by Nick

  I have a model that has paperclip attachments. The model might be used in multiple rails apps I need to return a full (non-relative) url to the attachment as part of a JSON API being consumed elsewhere. I'd like to abstract the paperclip aspect and have a simple virtual attribute like this: def thumbnail_url self.photo.url(:thumb) end This however only gives me the relative path. Since it's in the model I can't use the URL helper methods, right? What would be a good approach to prepending the application root url since I don't have helper support? I would like to avoid hardcoding something or adding code to the controller method that assembles my JSON. Thank you

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• Attribute lost with yield

  - by Nelson

  Here's an interesting one... There is some code that I'm trying to convert from IList to IEnumerable: [Something(123)] public IEnumerable<Foo> GetAllFoos() { SetupSomething(); DataReader dr = RunSomething(); while (dr.Read()) { yield return Factory.Create(dr); } } The problem is, SetupSomething() comes from the base class and uses: Attribute.GetCustomAttribute(new StackTrace().GetFrame(1).GetMethod(), typeof(Something)) Yield ends up creating MoveNext(), MoveNext() calls SetupSomething(), and MoveNext() does not have the [Something(123)] attribute. I can't change the base class, so it appears I am forced to stay with IList or implement IEnumerable manually (and add the attribute to MoveNext()). Is there any other way to make yield work in this scenario?

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• creational pattern for instances depending on multiple subclass instances

  - by markusw

  I have a problem, for that I was not able to identify a suitable design pattern. I want to create instances depending on a given type that has been passed to a factory method. What I am doing until now is the following: T create(SuperType x) { if (x instanceof SubType1) { // do some stuff and return a new SubType extends T } else if (x instanceof SubType2) { // do some stuff and return a new SubType extends T } else if ... } else { throw new UnSupportedOperationException("nothing defined for " + x); } } It seems not to be best pratice for me. Has anybody an idea how to solve this in a better way?

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• Is there any graphics library in a higher level than OpenGL

  - by Turtle

  Hello, I am looking for a graphics library for 3D reconstruction research to develop my specific viewer based on some library. OpenGL seems in a low level and I have to remake the wheel everywhere. And I also tried VTK(visualization toolkit). However, it seems too abstract that I need to master many conceptions before I start. Is there any other graphics library? I prefer to program in python. So I would like the library has a python wrapper. I think something like O3D would be better. But O3D is for javascript and it seems that Google already stops the development.

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• C# BinarySearch breaks when inheriting from something that implements IComparable<T>?

  - by Ender

  In .NET the BinarySearch algorithm (in Lists, Arrays, etc.) appears to fail if the items you are trying to search inherit from an IComparable instead of implementing it directly: List<B> foo = new List<B>(); // B inherits from A, which implements IComparable<A> foo.Add(new B()); foo.BinarySearch(new B()); // InvalidOperationException, "Failed to compare two elements in the array." Where: public abstract class A : IComparable<A> { public int x; public int CompareTo(A other) { return x.CompareTo(other.x); } } public class B : A {} Is there a way around this? Implementing CompareTo(B other) in class B doesn't seem to work.

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• Capturing USB Plug/Unplug events in Firemonkey

  - by radsdau

  [RAD Studio XE3 / C++] I have a FMX project running in Windows only at this stage, but I need to detect events when USB devices are connected and disconnected. I have a similar VCL app that can do this fine, but the Application-HookMainWindow is not exposed in FMX (only VCL). Is there an elegant way to handle this? Or do I have to hack some VCL stuff into my FMX app to make that work? I'd imagine I have to abstract it so I can support other platforms down the track. For the meantime though I need to get the Windows solution working. If the 'VCL hack' thing is required, how would I reference the vcl::Forms::Application from within my Fmx app? Cheers.

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• Recursive Function To Create Array

  - by mTuran

  Hi, i use kohana framework and i am trying to code recursive function to create category tree. My Categories Table id int(11) NO PRI NULL auto_increment name varchar(50) NO NULL parent_id int(11) NO NULL projects_count int(11) NO NULL My Example Which Is Not Work public static function category_list($parent_id = 0) { $result = Database::instance()->query(' SELECT name, projects_count FROM project_categories WHERE parent_id = ?', array($parent_id) ); $project_categories = array(); foreach($result as $row) { $project_categories[] = $row; Project_Categories_Model::factory()->category_list($parent_id + 1); } return $project_categories; }

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• Auto-Complete Suggestions in Source Code Editor

  - by Jim

  Hello, Most IDEs (Eclipse, Netbeans, Intelij) provide contextually smart suggestions about the current statement you're writing. We would like to do the same thing (In Java for Java). We considered tokenizing the input and building our own abstract syntax trees, but quickly realized that could be a month long project in and of its self. We also started digging through the source code for the above mentioned IDEs, but it appears (correct me if I'm wrong) that the auto-complete code is pretty tightly woven with the rest of the IDE. We're wondering if anyone knows of a relatively isolated package that we could pull into our project to provide this auto-complete functionality. Thanks!

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• how to call any method of Project from classlibrary?

  - by Pankaj Mishra

  Hello I have Class Library Where a class of multithreading Of Producer and consumer based. private void WorkDeQueue() { while (true) { string Url = null; lock (locker) { if (queueList.Count > 0) { Url = queueList.Dequeue(); /* return if a null is found in the queue */ if (Url == null) return; } } if (Url != null) { /* if a job was found then process it */ GetData(Url); //This Is a Method } else { /* if a job was not found (meaning list is empty) then * wait till something is added to it*/ wh.WaitOne(); } } } this GetData method has no body on that class. How can i call any method of my project in palace of getdata. I tried with factory Pattern and also with reflection. but both didn't worked for me. So plz tell me how can i call any method of my project from here.

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• How do I pass a DBNull value to a parameterized SELECT statement?

  - by Dan

  I have a SQL statement in C# (.NET Framework 4 running against SQL Server 2k8) that looks like this: SELECT [Column1] FROM [Table1] WHERE [Column2] = @Column2 The above query works fine with the following ADO.NET code: DbParameter parm = Factory.CreateDbParameter(); parm.Value = "SomeValue"; parm.ParameterName = "@Column2"; //etc... This query returns zero rows, though, if I assign DBNull.Value to the DbParameter's Value member even if there are null values in Column2. If I change the query to accommodate the null test specifically: SELECT [Column1] FROM [Table1] WHERE [Column2] IS @Column2 I get an "Incorrect syntax near '@Column2'" exception at runtime. Is there no way that I can use null or DBNull as a parameter in the WHERE clause of a SELECT statement?

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• how to translate Haskell into Scalaz?

  - by TOB

  One of my high school students and I are going to try to do a port of Haskell's Parsec parser combinator library into Scala. (It has the advantage over Scala's built-in parsing library that you can pass state around fairly easily because all the parsers are monads.) The first hitch I've come across is trying to figure out how Functor works in scalaz. Can someone explain how to convert this Haskell code: data Reply s u a = Ok a !(State s u) ParseError | Error ParseError instance Functor (Reply s u) where fmap f (Ok x s e) = Ok (f x) s e fmap _ (Error e) = Error e -- XXX into Scala (using Scalaz, I assume). I got as far as sealed abstract class Reply[S, U, A] case class Ok[S, U, A](a: A, state: State[S, U], error: ParseError) extends Reply[S, U, A] case class Error[S, U, A](error: ParseError) extends Reply[S, U, A] and know that I should make Reply extend the scalaz.Functor trait, but I can't figure out how to do that. (Mostly I'm having trouble figuring out what the F[_] parameter does.) Any help appreciated! Thanks, Todd

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• Is it possible to create ICriteria/ICriterion from LINQ or HQL?

  - by adrin

  I am creating a method that can create filter understood by NHibernate (by filter i mean a set of ICriteria object for example) from my abstract filter object. public static IEnumerable<ICriterion> ToNhCriteria(this MyCriteria criteria) { // T4 generated function // lots of result.Add(Expression.Or(Expression.Eq(),Expression.Eq)) expression trees - hard to generate // Is there a way to generate HQL/Linq query here istead? } then i want to do something like session.CreateCriteria<Entity>().Add(myCriteria.ToNhCriteria()) to filter entities. The problem is that using Expression. methods (Expression.Or etc) is quite tedious (the method is generated and i have multiple or statements that have to be joined into an expression somehow). Is there a way to avoid using Expression.Or() and create ICrietrion / ICriteria using LINQ or HQL?

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• [C++]Advantage of using a static member function instead of an equivalent non-static member function

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• Fastest method for SQL Server inserts, updates, selects

  - by Ian

  I use SPs and this isn't an SP vs code-behind "Build your SQL command" question. I'm looking for a high-throughput method for a backend app that handles many small transactions. I use SQLDataReader for most of the returns since forward only works in most cases for me. I've seen it done many ways, and used most of them myself. Methods that define and accept the stored procedure parameters as parameters themselves and build using cmd.Parameters.Add (with or without specifying the DB value type and/or length) Assembling your SP params and their values into an array or hashtable, then passing to a more abstract method that parses the collection and then runs cmd.Parameters.Add Classes that represent tables, initializing the class upon need, setting the public properties that represent the table fields, and calling methods like Save, Load, etc I'm sure there are others I've seen but can't think of at the moment as well. I'm open to all suggestions.

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• Lackadaisical One-to-One between Char and Byte Streams

  - by Vaibhav Bajpai

  I expected to have a one-to-one correspondence between the character streams and byte streams in terms of how the classes are organized in their hierarchy. FilterReader and FilterWriter (character streams) correspond back to FilterInputStream and FilterOutputStream (byte stream) classes. However I noticed few changes as - BufferedInputStream extends FilterInputStream, but BufferedReader does NOT extend FilterReader. BufferedOutputStream and PrintStream both extend FilterOutputStream, but BufferedWriter and PrintWriter does NOT extend FilterWriter. FilterInputStream and FilterOutputStream are not abstract classes, but FilterReader and FilterWriter are. I am not sure if I am being too paranoid to point out such differences, but was just curious to know if there was design reasoning behind such decision.

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• Code doesn't work in foreach

  - by Arlen Beiler

  Here is my code: var divarray = document.getElementById("yui-main").getElementsByTagName("div"); var articleHTML; var absHTML; var keyHTML; var bodyHTML = []; for( var i in divarray) { if(divarray[i].className == "articleBody"){ articleHTML = divarray[i]; for( var j in articleHTML ){ bodyHTML[i] = ''; if(articleHTML[j].className == "issueMiniFeature"){continue;} if(articleHTML[j].className == "abstract"){absHTML = articleHTML[i]; continue;} if(articleHTML[j].className == "journalKeywords"){keyHTML = articleHTML[i]; continue;} bodyHTML[i] = articleHTML[i]; } break; } i++; } The error I am getting is: SyntaxError: Unexpected token var I am using Google Chrome

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• Weird use of generics

  - by Karl Trumstedt

  After a bit of programming one of my classes used generics in a way I never seen before. I would like some opinions of this, if it's bad coding or not. abstract class Base<T> : where T : Base<T> { // omitted methods and properties. virtual void CopyTo(T instance) { /*code*/ } } class Derived : Base<Derived> { override void CopyTo(Derived instance) { base.CopyTo(instance); // copy remaining stuff here } } is this an OK use of generics or not? I'm mostly thinking about the constraint to "itself". I sometimes feel like generics can "explode" to other classes where I use the Base class.

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• Separate functionality depending on Role in ASP.NET MVC

  - by Andrew Bullock

  I'm looking for an elegant pattern to solve this problem: I have several user roles in my system, and for many of my controller actions, I need to deal with slightly different data. For example, take /Users/Edit/1 This allows a Moderator to edit a users email address, but Administrators to edit a user's email address and password. I'd like a design for separating the two different bits of action code for the GET and the POST. Solutions I've come up with so far are: Switch inside each method, however this doesn't really help when i want different model arguments on the POST :( Custom controller factory which chooses a UsersController_ForModerators and UsersController_ForAdmins instead of just UsersController from the controller name and current user role Custom action invoker which choose the Edit_ForModerators method in a similar way to above Have an IUsersController and register a different implementation of it in my IoC container as a named instance based on Role Build an implementation of the controller at runtime using Castle DynamicProxy and manipulate the methods to those from role-based implementations Im preferring the named IoC instance route atm as it means all my urls/routing will work seamlessly. Ideas? Suggestions?

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• Static nested class visibility issue with Scala / Java interop

  - by Matt R

  Suppose I have the following Java file in a library: package test; public abstract class AbstractFoo { protected static class FooHelper { public FooHelper() {} } } I would like to extend it from Scala: package test2 import test.AbstractFoo class Foo extends AbstractFoo { new AbstractFoo.FooHelper() } I get an error, "class FooHelper cannot be accessed in object test.AbstractFoo". (I'm using a Scala 2.8 nightly). The following Java compiles correctly: package test2; import test.AbstractFoo; public class Foo2 extends AbstractFoo { { new FooHelper(); } } The Scala version also compiles if it's placed in the test package. Is there another way to get it to compile?

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