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• The pImpl idiom and Testability

  - by Rimo

  The pImpl idiom in c++ aims to hide the implementation details (=private members) of a class from the users of that class. However it also hides some of the dependencies of that class which is usually regarded bad from a testing point of view. For example if class A hides its implementation details in Class AImpl which is only accessible from A.cpp and AImpl depends on a lot of other classes, it becomes very difficult to unit test class A since the testing framework has no access to the methods of AImpl and also no way to inject dependency into AImpl. This has been a problem for me lately and I am beginning to think that the pImpl idiom and writing testable code don't mix well. Has anyone come across this problem before? and have you found a solution?

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• Extending abstract classes in c#

  - by ng

  I am a Java developer and I have noticed some differences in extending abstract classes in c# as opposed to Java. I was wondering how a c# developer would achived the following. 1) Covarience public abstract class A { public abstract List<B> List(); } public class BList : List<T> where T : B { } public abstract class C : A { public abstract BList List(); } So in the above hierarchy, there is covarience in C where it returns a type compatible with what A returns. However this gives me an error in Visual Studio. Is there a way to specify a covarient return type in c#? 2) Adding a setter to a property public abstract class A { public abstract String Name { get; } } public abstract class B : A { public abstract String Name { get; set } } Here the compiler complains of hiding. Any suggestions? Please do not suggest using interfaces unless that is the ONLY way to do this.

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• GAE: Why are subclasses instances of db.Model (parent)?

  - by bryanallott

  Given: class A: pass class B(A): pass isinstance(B(), A) will return True. BUT class MyModel(db.Model): pass isinstance(MyModel(), db.Model) returns False(surely True?). What am I missing?

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• null reference problems with c#

  - by alex

  Hi: In one of my window form, I created an instance of a class to do some works in the background. I wanted to capture the debug messages in that class and displayed in the textbox in the window form. Here is what I did: class A //window form class { public void startBackGroundTask() { B backGroundTask = new B(this); } public void updateTextBox(string data) { if (data != null) { if (this.Textbox.InvokeRequired) { appendUIDelegate updateDelegate = new appendUIDelegate(updateUI); try { this.Invoke(updateDelegate, data); } catch (Exception e) { Console.WriteLine(e.Message); } } else { updateUI(data); } } } private void updateUI(string data) { if (this.Textbox.InvokeRequired) { this.Textbox.Invoke(new appendUIDelegate(this.updateUI), data); } else { //update the text box this.Textbox.AppendText(data); this.Textbox.AppendText(Environment.NewLine); } } private delegate void appendUIDelegate(string data); } class B // background task { A curUI; public b( A UI) { curUI = UI; } private void test() { //do some works here then log the debug message to UI. curUI.updateTextBox("message); } } I keep getting a null reference exception after this.Invoke(updateDelegate, data); is called. I know passing "this" as a parameter is strange. But I want to send the debug message to my window form. Please help. Thanks

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• how toaccess the attributes in another form? c#

  - by Chelsea_cole

  I have a problem in a same namespace: public partial class frmForm1 : Form // Form1 { public class Account { public string Username; public string Password; } public class ListAcc { public static int count = 0; private static List<Account> UserList; public static List<Account> Data() { return UserList; } } } public partial class frmForm2 : Form // Form2 { private void button2_Click(object sender, EventArgs e) { frmForm1.Account A; string m = frmForm1.ListAcc<A>.[0].Username; //ERROR } } How could i access the attributes (Username, Password...) in frmForm1? Someone help me? Thanks!

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• ZF2 namespace and file system

  - by user1918648

  I have standard Application module in ZF2. It's configured by default, I didn't change anything. I just added some stuff: module/ Application/ src/ Application/ Entity/ Product/ **Product.php** Controller/ **IndexController.php** Product.php namespace Application\Entity; class Product { } IndexController.php namespace Application\Controller; use Zend\Mvc\Controller\AbstractActionController; use Zend\View\Model\ViewModel; use Application\Entity\Product; class IndexController extends AbstractActionController { public function indexAction() { $product = new Product(); } } and I get following error: Fatal error: Class 'Application\Entity\Product' not found in \module\Application\src\Application\Controller\IndexController.php on line 20 I use the same namespace, but it doesn't see it. Why? P.S: If I will change Product.php to be the following: namespace Application\Entity\Product; class Product { } then in the IndexController.php the following code will be working: namespace Application\Controller; use Zend\Mvc\Controller\AbstractActionController; use Zend\View\Model\ViewModel; use Application\Entity\Product\Product; class IndexController extends AbstractActionController { public function indexAction() { $product = new Product(); } }

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• Joining the same model twice in a clean way, but making the code reusable

  - by Shako

  I have a model Painting which has a Paintingtitle in each language and a Paintingdescription in each language: class Painting < ActiveRecord::Base has_many :paintingtitles, :dependent => :destroy has_many :paintingdescriptions, :dependent => :destroy end class Paintingtitle < ActiveRecord::Base belongs_to :painting belongs_to :language end class Paintingdescription < ActiveRecord::Base belongs_to :painting belongs_to :language end class Language < ActiveRecord::Base has_many :paintingtitles, :dependent => :nullify has_many :paintingdescriptions, :dependent => :nullify has_many :paintings, :through => :paintingtitles end As you might notice, I reference the Language model from my Painting model via both the Paintingtitle model and Paintingdescription model. This works for me when getting a list of paintings with their title and description in a specific language: cond = {"paintingdescription_languages.code" => language_code, "paintingtitle_languages.code" => language_code} cond['paintings.publish'] = 1 unless admin paginate( :all, :select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"], :joins => " INNER JOIN paintingdescriptions ON (paintings.id = paintingdescriptions.painting_id) INNER JOIN paintingtitles ON (paintings.id = paintingtitles.painting_id) INNER JOIN languages paintingdescription_languages ON (paintingdescription_languages.id = paintingdescriptions.language_id) INNER JOIN languages paintingtitle_languages ON (paintingtitle_languages.id = paintingtitles.language_id) ", :conditions => cond, :page => page, :per_page => APP_CONFIG['per_page'], :order => "id DESC" ) Now I wonder if this is a correct way of doing this. I need to fetch paintings with their title and description in different functions, but I don't want to specify this long join statement each time. Is there a cleaner way, for instance making use of the has_many through? e.g. has_many :paintingdescription_languages, :through => :paintingdescriptions, :source => :language has_many :paintingtitle_languages, :through => :paintingtitles, :source => :language But if I implement above 2 lines together with the following ones, then only paintingtitles are filtered by language, and not the paintingdescriptions: cond = {"languages.code" => language_code} cond['paintings.publish'] = 1 unless admin paginate( :all, :select => ["paintings.id, paintings.publish, paintings.photo_file_name, paintingtitles.title, paintingdescriptions.description"], :joins => [:paintingdescription_languages, :paintingtitle_languages], :conditions => cond, :page => page, :per_page => APP_CONFIG['per_page'], :order => "id DESC" )

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• java.util.Observable, will clients complete executing their update() before continuing

  - by jax

  When I call: setChanged(); notifyObservers() on a java.until.Observable class, will all the listening Observer objects complete execution of their udpate() methods - assuming we are running in the same Thread - before the java.until.Observable class continues running? This is important because I will be sending a few messages through the notifyObservers(Object o) method in quick concession, it is important that each Observer class has finished its method before the new one though. I understand that the order of execution for each Observer class may vary when we call notifyObservers() - it is just important that the order of method execution for each individual instance is in order.

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• as3 this.graphics calls do nothing

  - by zzz

  class A: [SWF(width='800',height='600',frameRate='24')] public class A extends MovieClip { private var b:B; public function A(){ super(); b = new B(); addChild(b); addEventListener(Event.ENTER_FRAME, update); } private function update(e:Event):void { b.draw(); } } class B: public class B extends MovieClip { public function draw():void { //! following code works well if put in constructor, but not here this.graphics.beginFill(0xff0000); this.graphics.drawCircle(200,200,50); } } this.graphics calls do nothing in draw method, but work fine inside B`s constructor, what i am doing wrong ?

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• C# equivalent of typeof for fields

  - by rwallace

  With reflection, you can look up a class from a string at run time, but you can also say typeof(Foo) and get compile time type checking, auto completion etc. If what you want is a field not a class, you can look it up from a string at runtime, but if you want compile time type checking etc., is there anyway to say something like fieldof(Foo.Bar)? I know the name of both the class and the field in advance, and I want to be able to refer to the field at compile time rather than with a run-time string lookup.

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• gluNewQuadric() before opengl's initialization

  - by Schrödinger's cat

  Hello, I'm working on a c++ code that uses SDL/opengl. Is this possible to create a pointer to a quadric with 'gluNewQuadric()' before having initialized opengl with 'SDL_SetVideoMode'? The idea is to create a class with a (pointer to a) quadric class member that has to be instantiate before the 'SDL_SetVideoMode' call. This pointer is initialized in the class' constructor with a 'gluNewQuadric()' call.

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• Objects with inheritance memory storage

  - by nikitas350

  Say that i have some classes like this example. class A { int k, m; public: A(int a, int b) { k = a; m = b; } }; class B { int k, m; public: B() { k = 2; m = 3; } }; class C : private A, private B { int k, m; public: C(int a, int b) : A(a, b) { k = b; m = a; } }; Now, in a class C object, are the variables stored in a specific way? I know what happens in a POD object, but this is not a POD object...

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• Calling a constructor to reinitialize variables doesn't seem to work?

  - by Matt

  I wanted to run 1,000 iterations of a program, so set a counter for 1000 in main. I needed to reinitialize various variables after each iteration, and since the class constructor had all the initializations already written out - I decided to call that after each iteration, with the result of each iteration being stored in a variable in main. However, when I called the constructor, it had no effect...it took me a while to figure out - but it didn't reinitialize anything! I created a function exactly like the constructor - so the object would have its own version. When I called that, it reinitialized everything as I expected. int main() { Class MyClass() int counter = 0; while ( counter < 1000 ) { stuff happens } Class(); // This is how I tried to call the constructor initially. // After doing some reading here, I tried: // Class::Class(); // - but that didn't work either /* Later I used... MyClass.function_like_my_constructor; // this worked perfectly */ } ...Could someone try to explain why what I did was wrong, or didn't work, or was silly or what have you? I mean - mentally, I just figured - crap, I can call this constructor and have all this stuff reinitialized. Are constructors (ideally) ONLY called when an object is created?

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• final fields and thread-safety

  - by pcjuzer

  Should it be all fields, including super-fields, of a purposively immutable java class 'final' in order to be thread-safe or is it enough to have no modifier methods? Suppose I have a POJO with non-final fields where all fields are type of some immutable class. This POJO has getters-setters, and a constructor wich sets some initial value. If I extend this POJO with knocking out modifier methods, thus making it immutable, will extension class be thread-safe?

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• Java PropertyChangeListener

  - by Laphroaig

  Hi, i'm trying to figure out how to listen a property change on another class. this is my code: class with the property to listen: public class ClassWithProperty { private PropertyChangeSupport changes = new PropertyChangeSupport(this); private int usersOnline; public int getUsersOnline() { return usersOnline; } public ClassWithProperty() { usersOnline = 0; while (usersOnline<10) { changes.firePropertyChange("usersOnline", usersOnline, usersOnline++); } } public void addPropertyChangeListener( PropertyChangeListener l) { changes.addPropertyChangeListener(l); } public void removePropertyChangeListener( PropertyChangeListener l) { changes.removePropertyChangeListener(l); } } class where i need to know when the property change: public class Main { private static ClassWithProperty test; public static void main(String[] args) { test = new ClassWithProperty(); test.addPropertyChangeListener(listen()); } private static PropertyChangeListener listen() { System.out.println(test.getUsersOnline()); return null; } } I have the event fired only the last time (usersOnline=10). Sorry if it can be a stupid question, i'm learning now java and can't find a solution.

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• AJAX Closures and targeting 'this'

  - by Nick Lowman

  In the code example below the success callback function logs 'input#04.update' four times rather than each individual input, which makes sense seeing how closures work but how would I go about targeting each individual input using this. <input type="text" name="" id="01" class="update"> <input type="text" name="" id="02" class="update"> <input type="text" name="" id="03" class="update"> <input type="text" name="" id="04" class="update"> function updateFields(){ $('input.update').each(function(){ $this = $(this); $.ajax({ data: 'id=' + this.id, success: function(resp){ console.log($this); $this.val(resp) } }); }); }

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• Rails find through association

  - by yogi

  class Customer < ActiveRecord::Base has_one :address, :foreign_key => "customerid" end class Address < ActiveRecord::Base belongs_to :customer, :foreign_key => "customerid" end How do I find records in customer that do not have customerid in address table? in SQL i'd do select * from customer a, address b where a.customerid <> b.customerid

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• Ruby Regular Expressions - Checking the start middle and end of a line?

  - by Steven

  Hi, I need to get the "274.20p" out of: <td nowrap="nowrap" class="dataRegularUlOn" style="text-align: right;">274.20p</td> I would like to do regular expressions on: <td class="dataRegularUlOn" > so something like: /<td(.*?)class="dataRegularUlOn"(.*?)>/ I'm using ruby, on linux. thks

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• Deleting dynamic array of char in C++.

  - by anonymous

  I have this class, with the atribute 'word' class Node { char *word; Inside the Node constructor, I do this asignation: word = new char[strlen(someword)]; In the destructor of the Node class, I try to delete the contents pointed by word: delete []word; I obtain the next message after executing the programs: "Heap block at 003E4F48 modified at 003E4F51 past requested size of 1" What am I not doing well?

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• Using Visual Studio to make non aspx code-behind pages

  - by rizzle

  I want to build my own "code behind" like pages so that i can have HTML in a HTML file and code in cs file but be able to have Intellesense for the tokens in the HTML file. (i know that's what the .NET page class does, but i want to have something much lighter) EG: in the .html file: <%@ Directive classname="HTMLSnippet" %> <html> <body> <div>[%message%] </body> </html> and in a .cs file public class MyClass : HTMLSnippet { public class MyClass () { snippet.message = "message goes here" } } So my question is how do make the HTMLSnippet class so that it's members are automatically created, and specifically show up in Intellesense as i add tokens to the .html file? I know that .net currently does it by creating the designer.cs file and basically builds a class with all the elements from the page as it goes, and that would work fine but how can i get visual studio to generate that before compiling so that it shows up in Intellesense. Thanks! Clarification I'm not using this as a handler yet, i want to use this to have HTML snippets with tokens be usable in code as an object with properties. so almost like a custom control. I think what i have to do is create a VS add-in that waits for me to type tokens into an .html file then it automatically creates a .cs file with members for each token.

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• jquery 1.3 not(:first) problem in IE

  - by sunil-mand99

  Hi, i have 3 div tags of same class, <div class="redc"> <p>sdfs</p> </div> <div class="redc"> <p>sdfs</p> </div> <div class="redc"> <p>sdfs</p> </div> to select div other than first ,$(".redc:not(:first)") works fine in mozilla,but not in IE Please suggest any alternative for IE Note: vesion jquery 1.3

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• C++ Template Classes and Copy Construction

  - by themoondothshine

  Is there any way I can construct an new object from the given object if the template parameters of both objects are identical at run-time? For example: I have a template class with the declaration: template<typename _Type1, typename _Type2> class Object; Next, I have two instantiations of the template: template class Object<char, int>; template class Object<wchar_t, wint_t>; Now, I want to write a member function such as: template<typename _Type1, typename _Type2> Object<char, int> Object<_Type1, _Type2>::toCharObject() { if(__gnu_cxx::__are_same<_Type1, char>::__value) return *this; else { //Perform some kind of conversion and return an Object<char, int> } } I have tried a couple of techniques, such as using __gnu_cxx::__enable_if<__gnu_cxx::__are_same<_Type1, char>::__value, _Type1>::__type in a copy constructor for the Oject class, but I keep running into the error: error: conversion from ‘Object<wchar_t, wint_t>’ to non-scalar type ‘Object<char, int>’ requested Is there no way I can do this? Any help will be greatly appreciated!

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• A loop (while/foreach) with "offset" wrapping and

  - by DarkGhostHunter

  After applying what wrapping objects using math operator, I just tought it will be over. But no. By far. <?php $faces= array( 1 => '<div class="block">happy</div>', 2 => '<div class="block">sad</div>', (sic) 21 => '<div class="block">angry</div>' ); $i = 1; foreach ($faces as $face) { echo $face; if ($i == 3) echo '<div class="block">This is and ad</div>'; if ($i % 3 == 0) { echo "<br />"; // or some other wrapping thing } $i++; } ?> In the code I have to put and ad after the second one, becoming by that the third object. And then wrap the three all in a <div class="row"> (a br after won't work out by design reasons). I thought I will going back to applying a switch, but if somebody put more elements in the array that the switch can properly wrap, the last two remaining elements are wrapped openly. Can i add the "ad" to the array in the third position? That would make things simplier, only leaving me with guessing how to wrap the first and the third, the fourth and the sixth, an so on.

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• Avoiding instanceof in Java

  - by Mark Lutton

  Having a chain of "instanceof" operations is considered a "code smell". The standard answer is "use polymorphism". How would I do it in this case? There are a number of subclasses of a base class; none of them are under my control. An analogous situation would be with the Java classes Integer, Double, BigDecimal etc. if (obj instanceof Integer) {NumberStuff.handle((Integer)obj);} else if (obj instanceof BigDecimal) {BigDecimalStuff.handle((BigDecimal)obj);} else if (obj instanceof Double) {DoubleStuff.handle((Double)obj);} I do have control over NumberStuff and so on. I don't want to use many lines of code where a few lines would do. (Sometimes I make a HashMap mapping Integer.class to an instance of IntegerStuff, BigDecimal.class to an instance of BigDecimalStuff etc. But today I want something simpler.) I'd like something as simple as this: public static handle(Integer num) { ... } public static handle(BigDecimal num) { ... } But Java just doesn't work that way. I'd like to use static methods when formatting. The things I'm formatting are composite, where a Thing1 can contain an array Thing2s and a Thing2 can contain an array of Thing1s. I had a problem when I implemented my formatters like this: class Thing1Formatter { private static Thing2Formatter thing2Formatter = new Thing2Formatter(); public format(Thing thing) { thing2Formatter.format(thing.innerThing2); } } class Thing2Formatter { private static Thing1Formatter thing1Formatter = new Thing1Formatter(); public format(Thing2 thing) { thing1Formatter.format(thing.innerThing1); } } Yes, I know the HashMap and a bit more code can fix that too. But the "instanceof" seems so readable and maintainable by comparison. Is there anything simple but not smelly?

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• Problem with generics

  - by jess

  I have this code in base class protected virtual bool HasAnyStuff<TObject>(TObject obj) where TObject:class { return false; } In child class I am overriding protected override bool HasAnyStuff<Customer>(Customer obj) { //some stuff if Customer.sth etc return false; } I am getting this error '''Type parameter declaration must be an identifier not a type''' What is it I am doing wrong here?

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