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  • In Java, is it possible for a super constructor invocation actually invoke a constructor in the calling class?

    - by John Assymptoth
    Super constructor invocation definition: [Primary.] [NonWildTypeArguments] super ( ArgumentListopt ) ; A super constructor call can be prefixed by an Primary expression. Example (taken from JLS): class Outer { class Inner{ } } class ChildOfInner extends Outer.Inner { ChildOfInner() { (new Outer()).super(); // (new Outer()) is the Primary } } Does a Primary expression exist that makes the call to super() the invocation of a constructor of the calling class? Or Java prevents that?

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  • Passing parameter to base class constructor or using instance variable?

    - by deamon
    All classes derived from a certain base class have to define an attribute called "path". In the sense of duck typing I could rely upon definition in the subclasses: class Base: pass # no "path" variable here def Sub(Base): def __init__(self): self.path = "something/" Another possiblity would be to use the base class constructor: class Base: def __init__(self, path): self.path = path def Sub(Base): def __init__(self): super().__init__("something/") What would you prefer and why? Is there a better way?

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  • How do I unit test the methods in a method object?

    - by Sancho
    I've performed the "Replace Method with Method Object" refactoring described by Beck. Now, I have a class with a "run()" method and a bunch of member functions that decompose the computation into smaller units. How do I test those member functions? My first idea is that my unit tests be basically copies of the "run()" method (with different initializations), but with assertions between each call to the member functions to check the state of the computation. (I'm using Python and the unittest module.)

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  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

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  • Class definition thinks setting a variable is a Unit?

    - by DeLongey
    Writing out a Scala class and problem here is that the compiler thinks that the code is a unit not returning the proper value. It's a method used to set a property in the class: def setObject(`object`:StripeObject):StripeObject = { this.`object` = `object` } The error is: type mismatch; found : Unit required: com.stripe.StripeObject The full class is: case class EventData(var previousAttributes: HashMap[String,Object], var `object`:StripeObject) extends StripeObject { def getPreviousAttributes = { previousAttributes } def setPreviousAttributes(previousAttributes: HashMap[String, Object]) = { this.previousAttributes = previousAttributes } def getObject = { `object` } def setObject(`object`:StripeObject):StripeObject = { this.`object` = `object` } } How do I make sure it doesn't return a Unit?

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  • JUnit : Is there a way to skip a test belonging to a Test class's parent?

    - by Jon
    I have two classes: public abstract class AbstractFoobar { ... } and public class ConcreteFoobar extends AbstractFoobar { ... } I have corresponding test classes for these two classes: public class AbstractFoobarTest { ... } and public class ConcreteFoobarTest extends AbstractFoobarTest { ... } When I run ConcreteFoobarTest (in JUnit), the annotated @Test methods in AbstractFoobarTest get run along with those declared directly on ConcreteFoobarTest because they are inherited. Is there anyway to skip them?

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  • How could I know if an object is derived from a specific generic class?

    - by Edison Chuang
    Suppose that I have an object then how could I know if the object is derived from a specific generic class. For example: public class GenericClass<T> { } public bool IsDeriveFrom(object o) { return o.GetType().IsSubclassOf(typeof(GenericClass)); //will throw exception here } please notice that the code above will throw an exception. The type of the generic class cannot be retrieved directly because there is no type for a generic class without a type parameter provided.

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  • C++ Pass a hidden arg to a class constructor?

    - by JP
    I would like to define a class that accept the pointer to it's parent class as an Argument, but would it be possible to somehow pass it without needing to pass it directly such as: class Child { public: Child(Parent* hiddenArg); }; class Parent { public: Child myChild; }; I know this is weird, but I am making my own Signal/Slot implementation and Child would be a signal defined, but I would like to get the parent so I can use it's Event Dispatcher...

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  • Working with Jquery. How to change css class of an element in same root

    - by Shantanu Gupta
    I want to change css class of an element on certain event in jquery. eg. focusin: function() { if(this.val()=="First Name") $(this).find("span ").css } $(this).find("span which contains _set").class= mycssclass here I want to change the CSS class of span element whose id contains "_set" as a part of substring in class name and also want to change the text i.e. InnerHtml property of javascript of this span element

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  • How do I mock/fake/replace/stub a base class at unit-test time in C#?

    - by MatthewMartin
    UPDATE: I've changed the wording of the question. Previously it was a yes/no question about if a base class could be changed at runtime. I may be working on mission impossible here, but I seem to be getting close. I want to extend a ASP.NET control, and I want my code to be unit testable. Also, I'd like to be able to fake behaviors of a real Label (namely things like ID generation, etc), which a real Label can't do in an nUnit host. Here a working example that makes assertions on something that depends on a real base class and something that doesn't-- in a more realistic unit test, the test would depend on both --i.e. an ID existing and some custom behavior. Anyhow the code says it better than I can: public class LabelWrapper : Label //Runtime //public class LabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } //Ugh, now I have to test FakeLabelWrapper public class FakeLabelWrapper : FakeLabel //Unit Test time { private readonly LabelLogic logic= new LabelLogic(); public override string Text { get { return logic.ProcessGetText(base.Text); } set { base.Text=logic.ProcessSetText(value); } } } [TestFixture] public class UnitTest { [Test] public void Test() { //Wish this was LabelWrapper label = new LabelWrapper(new FakeBase()) LabelWrapper label = new LabelWrapper(); //FakeLabelWrapper label = new FakeLabelWrapper(); label.Text = "ToUpper"; Assert.AreEqual("TOUPPER",label.Text); StringWriter stringWriter = new StringWriter(); HtmlTextWriter writer = new HtmlTextWriter(stringWriter); label.RenderControl(writer); Assert.AreEqual(1,label.ID); Assert.AreEqual("<span>TOUPPER</span>", stringWriter.ToString()); } } public class FakeLabel { virtual public string Text { get; set; } public void RenderControl(TextWriter writer) { writer.Write("<span>" + Text + "</span>"); } } //System Under Test internal class LabelLogic { internal string ProcessGetText(string value) { return value.ToUpper(); } internal string ProcessSetText(string value) { return value.ToUpper(); } }

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  • Class Template Instantiation: any way round this circular reference?

    - by TimYorke34
    I have two classes that I'm using to represent some hardware: A Button and an InputPin class which represent a button that will change the value of an IC's input pin when it's pressed down. A simple example of them is: template <int pinNumber> class InputPin { static bool IsHigh() { return ( (*portAddress) & (1<<pinNumber) ); } }; template <typename InputPin> class Button { static bool IsPressed() { return !InputPin::IsHigh(); } }; This works beautifully and by using class templates, the condition below will compile as tightly as if I'd handwritten it in assembly (a single instruction). Button < InputPin<1> > powerButton; if (powerButton.IsPressed()) ........; However, I am extending it to deal with interrupts and have got a problem with circular references. Compared to the original InputPin, a new InputPinIRQ class has an extra static member function that will be called automatically by the hardware when the pin value changes. I'd like it to be able to notify the Button class of this, so that the Button class can then notify the main application that it has been pressed/released. I am currently doing this with function pointers to callbacks. In order for the callback code to be inlined by the compiler, I need to pass the function pointers as template parameters. So now, both of the new classes have an extra template parameter that is a pointer to a callback function. Unfortunately this gives me a circular reference because to instantiate a ButtonIRQ class I now have to do something like this: ButtonIRQ< InputPinIRQ< A1, ButtonIRQ<....>::OnPinChange, OnButtonChange > pB; where the <...... represents the circular reference. Does anyone know how I can avoid this circular reference? I am new to templates, so might be missing something really simple. It's important that the compiler knows exactly what code will be run when the interrupt occurs as it then does some very useful optimisation - it is able to inline the callback function and literally inserts the callback function's code at the exact address that is called on a h/w interrupt.

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  • Python : How to intercept a method call which does-not exists?

    - by Yugal Jindle
    I want to create a class that doesn't gives an Attribute Error on call of any method that may or may not exists: My class: class magic_class: ... # How to over-ride method calls ... Expected Output: ob = magic_class() ob.unknown_method() # Prints 'unknown_method' was called ob.unknown_method2() # Prints 'unknown_method2' was called Now, unknown_method and unknown_method2 doesn't actually exists in the class, but how can we intercept the method call in python ?

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  • how can I get around no arrays as class constants in php?

    - by user151841
    I have a class with a static method. There is an array to check that a string argument passed is a member of a set. But, with the static method, I can't reference the class property in an uninstantiated class, nor can I have an array as a class constant. I suppose I could hard code the array in the static method, but then if I need to change it, I'd have to remember to change it in two places. I'd like to avoid this.

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  • How can I check if an object has a specific method?

    - by Ghommey
    I want to use a method of an object. Like $myObject->helloWorld(). However there are a couple of methods so I loop through an array of method names and call the method like this: my $methodName ="helloWorld"; $myObject->$methodNames; This works quite nice but some objects don't have all methods. How can I tell whether $myObject has a method called helloWorld or not?

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  • Custom base class for workflow activity , how to declare dependecy property ?

    - by Ajax2020
    Generally we derive custom activity from Activity or CompositeActivity class, i want to have my custom base class for all activities : like public class BusinessActivity : Activity { } then my custom activities will derive from BusinessActivity . The quetions is if i want ErrorMessageProperty and RetryCountProperty as dependency properties then in the BusinessActivity how to declare third param in Register method like public static DependencyProperty RetryCountProperty = DependencyProperty.Register("RetryCount", typeof(int), typeof(**BusinessActivity**)); What will happen if i derive from BusinessActivity class ?

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  • Should I create my own Assert class based on these reasons?

    - by Mike
    The main reason I don't like Debug.Assert is the fact that these assertions are disabled in Release. I know that there's a performance reason for that, but at least in my situation I believe the gains would outweigh the cost. (By the way, I'm guessing this is the situation in most cases). And yes, I know that you can use Trace.Assert instead. But even though that would work, I find the name Trace distracting, since I don't see this as tracing. The other reason to create my own class is laziness I guess, since I could write methods for the most usual cases like Assert.IsNotNull, Assert.Equals and so forth. The second part of my question has to do with using Environment.FailFast in this class. Would that be a good idea? I do like the ideas put forth in this document. That's pretty much where I got the idea from. One last point. Does creating a design like this imply having an untestable code path, as described in this answer by Eric Lippert on a different (but related) question?

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  • Is defining every method/state per object in a series of UML diagrams representative of MDA in general?

    - by Max
    I am currently working on a project where we use a framework that combines code generation and ORM together with UML to develop software. Methods are added to UML classes and are generated into partial classes where "stuff happens". For example, an UML class "Content" could have the method DeleteFromFileSystem(void). Which could be implemented like this: public partial class Content { public void DeleteFromFileSystem() { File.Delete(...); } } All methods are designed like this. Everything happens in these gargantuan logic-bomb domain classes. Is this how MDA or DDD or similar usually is done? For now my impression of MDA/DDD (which this has been called by higherups) is that it severely stunts my productivity (everything must be done The Way) and that it hinders maintenance work since all logic are roped, entrenched, interspersed into the mentioned gargantuan bombs. Please refrain from interpreting this as a rant - I am merely curious if this is typical MDA or some sort of extreme MDA UPDATE Concerning the example above, in my opinion Content shouldn't handle deleting itself as such. What if we change from local storage to Amazon S3, in that case we would have to reimplement this functionality scattered over multiple places instead of one single interface which we can provide a second implementation for.

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  • Create a thread in xna Update method to find path?

    - by Dan
    I am trying to create a separate thread for my enemy's A* pathfinder which will give me a list of points to get to the player. I have placed the thread in the update method of my enemy. However this seems to cause jittering in the game every-time the thread is called. I have tried calling just the method and this works fine. Is there any way I can sort this out so that I can have the pathfinder on its own thread? Do I need to remove the thread start from the update and start it in the constructor? Is there any way this can work. Here is the code at the moment: bool running = false; bool threadstarted; System.Threading.Thread thread; public void update() { if (running == false && threadstarted == false) { thread = new System.Threading.Thread(PathThread); //thread.Priority = System.Threading.ThreadPriority.Lowest; thread.IsBackground = true; thread.Start(startandendobj); //PathThread(startandendobj); threadstarted = true; } } public void PathThread(object Startandend) { object[] Startandendarray = (object[])Startandend; Point startpoint = (Point)Startandendarray[0]; Point endpoint = (Point)Startandendarray[1]; bool runnable = true; // Path find from 255, 255 to 0,0 on the map foreach(Tile tile in Map) { if(tile.Color == Color.Red) { if (tile.Position.Contains(endpoint)) { runnable = false; } } } if(runnable == true) { running = true; Pathfinder p = new Pathfinder(Map); pathway = p.FindPath(startpoint, endpoint); running = false; threadstarted = false; } }

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  • Examples of bad variable names and reasons [on hold]

    - by user470184
    I'll start with a class in the jdk package : public final class Sdp { should be : public final class SocketsDirectProtocol { Sdp is class name, this is ambigious, should be : Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); should be : Class<?> clazz = Class.forName("java.net.SdpSocketImpl", true, null); cl is ambiguous private static void setAccessible(final AccessibleObject o) { should be : private static void setAccessible(final AccessibleObject accessibleObject) { There are various other examples in this class, do you have similar and/or differing examples of variables that were named badly ? package com.oracle.net; public final class Sdp { private Sdp() { } /** * The package-privage ServerSocket(SocketImpl) constructor */ private static final Constructor<ServerSocket> serverSocketCtor; static { try { serverSocketCtor = (Constructor<ServerSocket>) ServerSocket.class.getDeclaredConstructor(SocketImpl.class); setAccessible(serverSocketCtor); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } /** * The package-private SdpSocketImpl() constructor */ private static final Constructor<SocketImpl> socketImplCtor; static { try { Class<?> cl = Class.forName("java.net.SdpSocketImpl", true, null); socketImplCtor = (Constructor<SocketImpl>)cl.getDeclaredConstructor(); setAccessible(socketImplCtor); } catch (ClassNotFoundException e) { throw new AssertionError(e); } catch (NoSuchMethodException e) { throw new AssertionError(e); } } private static void setAccessible(final AccessibleObject o) { AccessController.doPrivileged(new PrivilegedAction<Void>() { public Void run() { o.setAccessible(true); return null; } }); } /** * SDP enabled Socket. */ private static class SdpSocket extends Socket { SdpSocket(SocketImpl impl) throws SocketException { super(impl); } } /** * Creates a SDP enabled SocketImpl */ private static SocketImpl createSocketImpl() { try { return socketImplCtor.newInstance(); } catch (InstantiationException x) { throw new AssertionError(x); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { throw new AssertionError(x); } } /** * Creates an unconnected and unbound SDP socket. The {@code Socket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new Socket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static Socket openSocket() throws IOException { SocketImpl impl = createSocketImpl(); return new SdpSocket(impl); } /** * Creates an unbound SDP server socket. The {@code ServerSocket} is * associated with a {@link java.net.SocketImpl} of the system-default type. * * @return a new ServerSocket * * @throws UnsupportedOperationException * If SDP is not supported * @throws IOException * If an I/O error occurs */ public static ServerSocket openServerSocket() throws IOException { // create ServerSocket via package-private constructor SocketImpl impl = createSocketImpl(); try { return serverSocketCtor.newInstance(impl); } catch (IllegalAccessException x) { throw new AssertionError(x); } catch (InstantiationException x) { throw new AssertionError(x); } catch (InvocationTargetException x) { Throwable cause = x.getCause(); if (cause instanceof IOException) throw (IOException)cause; if (cause instanceof RuntimeException) throw (RuntimeException)cause; throw new RuntimeException(x); } } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new SocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs. */ public static SocketChannel openSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newSocketChannel(fd); } /** * Opens a socket channel to a SDP socket. * * <p> The channel will be associated with the system-wide default * {@link java.nio.channels.spi.SelectorProvider SelectorProvider}. * * @return a new ServerSocketChannel * * @throws UnsupportedOperationException * If SDP is not supported or not supported by the default selector * provider * @throws IOException * If an I/O error occurs */ public static ServerSocketChannel openServerSocketChannel() throws IOException { FileDescriptor fd = SdpSupport.createSocket(); return sun.nio.ch.Secrets.newServerSocketChannel(fd); } }

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