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• accessing base class's method with derived class's object which has a method of same name.

  - by ashish yadav

  when accessing foo() of "base" using derived class's object. include class base { public: void foo() { std::cout<<"\nHello from foo\n"; } }; class derived : public base { public: void foo(int k) { std::cout<<"\nHello from foo with value = "< } how to access base class method having a method of same name in derived class. the error generated has been shown. i apologize if i am not clear but i feel i have made myself clear as water. thanks in advance.

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• Inherit static properties in subclass without redeclaration?

  - by David

  Hi, I'm having the same problem as this guy with the application I'm writing right now. The problem is that static properties are not being inherited in subclasses, and so if I use the static:: keyword in my main class, it sets the variable in my main class as well. It works if I redeclare the static variables in my subclass, but I expect to have a large number of static properties and subclasses and wish to avoid code duplication. The top-rated response on the page I linked has a link to a few "workarounds", but it seems to have 404'd. Can anyone lend me some help or perhaps point me in the direction of said workarounds?

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• method __getattr__ is not inherited from parent class

  - by ??????

  Trying to subclass mechanize.Browser class: from mechanize import Browser class LLManager(Browser, object): IS_AUTHORIZED = False def __init__(self, login = "", passw = "", *args, **kwargs): super(LLManager, self).__init__(*args, **kwargs) self.set_handle_robots(False) But when I make something like this: lm["Widget[LinksList]_link_1_title"] = anc then I get an error: Traceback (most recent call last): File "<pyshell#8>", line 1, in <module> lm["Widget[LinksList]_link_1_title"] = anc TypeError: 'LLManager' object does not support item assignment Browser class have overridden method __getattr__ as shown: def __getattr__(self, name): # pass through _form.HTMLForm methods and attributes form = self.__dict__.get("form") if form is None: raise AttributeError( "%s instance has no attribute %s (perhaps you forgot to " ".select_form()?)" % (self.__class__, name)) return getattr(form, name) Why my class or instance don't get this method as in parent class?

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• Ruby get inheriting class

  - by Brian D.

  I'm working on creating my first plugin for rails. I'm still pretty new to ruby and I was wondering if its possible to get the inheriting class? For example, I'm trying to create a plugin that will allow unit testing and functional testing when you are not using migrations. What I'm trying to do is initialize a class variable named controller to be initialized to the type of controller that is being tested. If I have a base class ControllerTest: class ControllerTest < Test::Unit::TestCase attr_accessor :controller def initialize super @controller = "call function that will find the inheriting classes name and create an instance of that controller type." end end So what I'm currently stuck on is getting the name of the inheriting class. Is this possible? And if not, does anyone know another way on how I could go about implementing this? Thanks in advance.

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• custom TreeNode and SelectNodeChanged

  - by gilloux

  Hello, I'm working on asp.net I've written a custom Treenode (customTreeNode) that I use to populate a treeview the problem comes up when firing the selectnodechanged event this event give me a TreeNode object and not a customTreeNode and I cannot seem to cast it somehow, does sy have a clue ? Thx here is the code I have populate my tree node.ChildNodes.Add ( customTreeNode = new customTreeNode(site) ); customTreeNode public class customTreeNode : TreeNode { public Guid Id { get; set; } private SPWebEntry _dataContext; public SPWebEntry DataContext { get { return _dataContext; } } public customTreeNode(SPWebEntry DataContext) { _dataContext = DataContext; this.Text = _dataContext.Title; this.Id = _dataContext.Id; } } and the event void treeViewSiteCollection_SelectedNodeChanged(object sender, EventArgs e) { treeViewSiteCollection.SelectedNode; } treeViewSiteCollection.SelectedNode is of type TreeNode and I cannot cast it. Thx guys

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• Why can I not add a set accessor to an overriden property?

  - by Svish

  In a base class I have this property: public virtual string Text { get { return text; } } I want to override that and return a different text, but I would also like to be able to set the text, so I did this: public override string Text { get { return differentText; } set { differentText = value; } } This however does not work. I get a red squiggly under set saying that I can not override because it does not have a set accessor. Why is this aproblem? What should I do?

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• C# Hiding, overriding and calling function from base class.

  - by Lukasz Lysik

  I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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• Qt - invalid conversion to child class

  - by David Davidson

  I'm drawing polygons using the Graphics View framework. I added a polygon to the scene with this: QGraphicsPolygonItem *poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); poly->setPos(some_point); But I need to implement some custom behaviour like selection, mouse over indicator, and other similar stuff on the graphics item. So I declared a class that inherits QGraphicsPolygonItem: #include <QGraphicsPolygonItem> class GridHex : public QGraphicsPolygonItem { public: GridHex(QGraphicsItem* parent = 0); }; GridHex::GridHex(QGraphicsItem* parent) : QGraphicsPolygonItem(parent) { } Not doing much with that class so far, as you can see. But shouldn't replacing QGraphicsPolygonItem with my GridHex class? This is throwing a " invalid conversion from 'QGraphicsPolygonItem*' to 'GridHex*' " error: GridHex* poly = scene->addPolygon(QPolygonF(vector_of_QPointF)); What am I doing wrong?

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• C#: How to inherit constructors?

  - by Ian Boyd

  Imagine a base class with many constructors and a virtual method public class Foo { ... public Foo() {...} public Foo(int i) {...} ... public virtual void SomethingElse() {...} ... } and now I want to create a descendant class that overrides the virtual method: public class Bar : Foo { public override void SomethingElse() {...} } And another descendant that does some more stuff: public class Bah : Bar { public void DoMoreStuff() {...} } Do I really have to copy all constructors from Foo into Bar and Bah? And then if I change a constructor signature in Foo, do I have to update it in Bar and Bah? Is there no way to inherit constructors? Is there no way to encourage code reuse?

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• XSD: xs:sequence & xs:choice combination for xs:extension elements?

  - by bguiz

  Hi, My question is about defining an XML schema that will validate the following sample XML: <rules> <other>...</other> <bool>...</bool> <other>...</other> <string>...</string> <other>...</other> </rules> The order of the child nodes does not matter. The cardinality of the child nodes is 0..unbounded. All the child elements of the rules node have a common base type, rule, like so: <xs:complexType name="booleanRule"> <xs:complexContent> <xs:extension base="rule"> ... </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="stringFilterRule"> <xs:complexContent> <xs:extension base="filterRule"> ... </xs:extension> </xs:complexContent> </xs:complexType> My current attempt at defining the schema for the rules node is below. However, Can I nest xs:choice within xs:sequence? If, where do I specify the maxOccurs="unbounded" attribute? Is there a better way to do this, such as an xs:sequence which specifies only the base type of its child elements? <xs:element name="rules"> <xs:complexType> <xs:sequence> <xs:choice> <xs:element name="bool" type="booleanRule" /> <xs:element name="string" type="stringRule" /> <xs:element name="other" type="someOtherRule" /> </xs:choice> </xs:sequence> </xs:complexType> </xs:element>

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• How can I extend PHP DOMElement?

  - by Michael Tsang

  a.php #!/usr/bin/php <?php class HtmlTable extends DOMElement { public function __construct($height, $width) { parent::__construct("table"); for ($i = 0; $i < $height; ++$i) { $row = $this->appendChild(new DOMElement("tr")); for($j = 0; $j < $width; ++$j) { $row->appendChild(new DOMElement("td")); } } } } $document = new DOMDocument("1.0", "UTF-8"); $document->registerNodeClass("DOMElement", "HtmlTable"); $document->appendChild(new HtmlTable(3, 2)); $document->saveXML(); Running it gets Fatal error: Uncaught exception 'DOMException' with message 'No Modification Allowed Error' in /home/www/a.php:9 Stack trace: #0 /home/www/a.php(9): DOMNode->appendChild(Object(DOMElement)) #1 /home/www/a.php(19): HtmlTable->__construct(3, 2) #2 {main} thrown in /home/www/a.php on line 9

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• Why is F# member not found when used in subclass

  - by James Black

  I have a base type that I want to inherit from, for all my DAO objects, but this member gets the error further down about not being defined: type BaseDAO() = member v.ExecNonQuery2(conn)(sqlStr) = let comm = new MySqlCommand(sqlStr, conn, CommandTimeout = 10) comm.ExecuteNonQuery |> ignore comm.Dispose |> ignore I inherit in this type: type CreateDatabase() = inherit BaseDAO() member private self.createDatabase(conn) = self.ExecNonQuery2 conn "DROP DATABASE IF EXISTS restaurant" This is what I see when my script runs in the interactive shell: --> Referenced 'C:\Program Files\MySQL\MySQL Connector Net 6.2.3\Assemblies\MySql.Data.dll' [Loading C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\BaseDAO.fs] namespace FSI_0106.RestaurantServiceDAO type BaseDAO = class new : unit -> BaseDAO member ExecNonQuery2 : conn:MySql.Data.MySqlClient.MySqlConnection -> sqlStr:string -> unit member execNonQuery : sqlStr:string -> unit member execQuery : sqlStr:string * selectFunc:(MySql.Data.MySqlClient.MySqlDataReader -> 'a list) -> 'a list member f : x:obj -> string member Conn : MySql.Data.MySqlClient.MySqlConnection end [Loading C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\CreateDatabase.fs] C:\Users\jblack\Documents\Visual Studio 2010\Projects\RestaurantService\RestaurantDAO\CreateDatabase.fs(56,14): error FS0039: The field, constructor or member 'ExecNonQuery2' is not defined I am curious what I am doing wrong. I have tried not inheriting, and just instantiating the BaseDAO type in the function, but I get the same error. I started on this path because I had a property that had the same error, so it seems there may be a problem with how I am defining my BaseDAO type, but it compiles with no error, which further confuses me about this problem.

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• With this generics code why am I getting "Argument 1: cannot convert from 'ToplogyLibrary.Relationsh

  - by Greg

  Hi, Any see why I'm getting a "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase' to 'TRelationship'" in the code below, in CreateRelationship() ? public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, TNode> Nodes { get; private set; } public List<TRelationship> Relationships { get; private set; } // Constructors protected TopologyBase() { Nodes = new Dictionary<TKey, TNode>(); Relationships = new List<TRelationship>(); } // Methods public TNode CreateNode(TKey key) { var node = new TNode {Key = key}; Nodes.Add(node.Key, node); return node; } public void CreateRelationship(TNode parent, TNode child) { // Validation if (!Nodes.ContainsKey(parent.Key) || !Nodes.ContainsKey(child.Key)) { throw new ApplicationException("Can not create relationship as either parent or child was not in the graph: Parent:" + parent.Key + ", Child:" + child.Key); } // Add Relationship var r = new RelationshipBase<TNode>(); r.Parent = parent; r.Child = child; Relationships.Add(r); // *** HERE *** "Argument 1: cannot convert from 'ToplogyLibrary.RelationshipBase<TNode>' to 'TRelationship'" } } public class RelationshipBase<TNode> { public TNode Parent { get; set; } public TNode Child { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } }

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• How to invalidate / refresh a domain instance association?

  - by Kimble

  There is a bug in Grails preventing me from using removeFrom* when the node I'm trying to remove is extending the collection type. Removing the node directly from the association won't update the second level cache. A hasMany B Is there any way to manually invalidate or force a reload on an association cache? Invoking refresh() on the many side didn't do the trick.

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• Placement of a call to the parent method

  - by Alejandro

  I have a class that has a method. That class has a child class that overrides that method. The child's method has to call the parent's method. In all OO that I've seen or written calls to the parent's version of the same method were on the first line of the method. On a project that I am working on circumstances call for placing that method call at the end of a method. Should I be worried? Is that a code smell? Is this code inherently bad? class Parent { function work() { // stuff } } class Child { function work() { // do thing 1 // do thing 2 parent::work(); // is this a bad practice? // should I call the parent's work() method before // I do anything in this method? } }

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• Convert Subclass to Inherited Class

  - by Dave

  I have a C# .NET 2.0 project A that has a form (TreeForm) that uses Tree objects. I have a project B that has a class Oak that inherits Tree. When I try to reference and use the TreeForm in project B with my Oak objects, it's looking for objects of type Tree. I've tried casting the Oak objects to Tree, but I get the error "Cannot convert type Oak to Tree". How can I use my Oak objects in the TreeForm from project A?

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• Maven: trying to get my submodule's poms to NOT inherit a plugin in the parent

  - by jobrahms

  My project has a parent pom and several submodule poms. I've put a plugin in the parent that is responsible for building our installer distributables (using install4j). It doesn't make sense to have this plugin run on the submodules, so I've put false in the plugin's config, as seen below. The problem is, when I run mvn clean install install4j:compile it cleans, compiles, and runs the install4j plugin on the parent, but then it tries to run it on the child modules and crashes. Here's the plugin config <plugin> <groupId>com.google.code.maven-install4j</groupId> <artifactId>maven-install4j-plugin</artifactId> <version>0.1.1</version> <inherited>false</inherited> <configuration> <executable>${devenv.install4jc}</executable> <configFile>${basedir}/newinstaller/ehd-demo.install4j</configFile> <releaseId>${project.version}</releaseId> <attach>false</attach> <skipOnMissingExecutable>true</skipOnMissingExecutable> </configuration> </plugin> Am I misunderstanding the purpose of inherited=false? What is the correct way to get this to work? I'm using maven 2.2.0.

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• ASP.NET MVC 3 embrace dynamic type - CSDN.NET - CSDN Software Development Channel

  - by user559071

  About a decade ago, Microsoft will all bet on the WebForms and static types. With the complete package from scattered to the continuous development, and now almost every page can be viewed as its own procedure. Subsequent years, the industry continued to move in another direction, love is better than separation package, better than the late binding early binding to the idea. This leads to two very interesting questions. The first is the problem of terminology. Consider the original Smalltalk MVC model, view and controller is not only tightly coupled together, and usually in pairs. Most of the framework is that Microsoft, including the classic VB, WinForms, WebForms, WPF and Silverlight, they both use the code behind file to store the controller logic. But said "MVC" usually refers to the view and controller are loosely coupled framework. This is especially true for the Web framework, HTML form submission mechanism allows any views submitted to any of the controller. Since this article was mainly talking about Web technologies, so we need to use the modern definition. The second question is "If you're Microsoft, how to change orbit without causing too much pressure to the developer?" So far, the answer is: new releases each year, until the developers meet up. ASP.NET MVC's first product was released last March. Released in March this year, ASP.NET MVC 2.0. 3.0 RC 2 is currently in phase, expected to be released next March. December 10, Microsoft released ASP.NET MVC 3.0 Release Candidate 2. RC 2 is built on top of Microsoft's commitment to the jQuery: The default project template into jQuery 1.4.4, jQuery Validation 1.7 and jQuery UI. Although people think that Microsoft will focus shifted away from server-side controls to be a joke, but the introduction of Microsoft's jQuery UI is that this is the real thing. For those worried about the scalability of the developers, there are many excellent control can replace the session state. With SessionState property, you can tell the controller session state is read-only, read-write, or can be completely ignored in the. This site is no single server, but if a server needs to access another server session state, then this approach can provide a great help. MVC 3 contains Razor view engine. By default, the engine will be encoded HTML output, so that we can easily output on the screen the text of the original. HTML injection attacks even without the risk of encoded text can not easily prevent the page rendering. For many C # developers in the end do what is most shocking that MVC 3 for the controller and view and embrace the dynamic type. ViewBag property will open a dynamic object, developers can run on top of the object to add attributes. In general, it is used to send the view from the controller non-mode data. Scott Guthrie provides state of the sample contains text (such as the current time) and used to assemble the list box entries. Asked Link: http://www.infoq.com/cn/news/2010/12/ASPNET-MVC-3-RC-2; jsessionid = 3561C3B7957F1FB97848950809AD9483

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• Returning a C++ reference in a const member functionasses

  - by Chris Kaminski

  A have a class hierarchy that looks somethign like this: class AbstractDataType { public: virtual int getInfo() = 0; }; class DataType: public AbstractDataType { public: virtual int getInfo() { }; } class Accessor { DataType data; public: const AbstractDataType& getData() const { return(data); } } Well, GCC 4.4 reports: In member function ‘const AbstractDataType& Accessor::getData() const’: error: invalid initialization of reference of type ‘const AbstractDataType&’ from expression of type ‘const DataType’ Where am I going wrong - is this a case where I MUST use a pointer?

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• How to inherit events between objects

  - by marduck19

  I need inherit events and properties for example move a picture around the form Y have this code to move the picture but y need create multiple images with the same behavior private void pictureBox_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { x = e.X; y = e.Y; } } private void pictureBox_MouseMove(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { pictureBox.Left += (e.X -x); pictureBox.Top += (e.Y - y); } }

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• Can I "inherit" a delegate? Looking for ways to combine Moq and MSpec without conflicts around It...

  - by Tomas Lycken

  I have started to use MSpec for BDD, and since long ago I use Moq as my mocking framework. However, they both define It, which means I can't have using Moq and using Machine.Specifications in the same code file without having to specify the namespace explicitly each time I use It. Anyone who's used MSpec knows this isn't really an option. I googled for solutions to this problem, and this blogger mentions having forked MSpec for himself, and implemented paralell support for Given, When, Then. I'd like to do this, but I can't figure out how to declare for example Given without having to go through the entire framework looking for references to Establish, and changing code there to match that I want either to be OK. For reference, the Establish, Because and It are declared in the following way: public delegate void Establish(); public delegate void Because(); public delegate void It(); What I need is to somehow declare Given, so that everywhere the code looks for an Establish, Given is also OK.

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• wcf class implementing multiple service contracts

  - by Archie

  Hello, I have a class TestService which implements two service contracts called IService1 and IService2. But I'm facing a difficulty in implementation. My Code looks as follows: Uri baseAddress = new Uri("http://localhost:8000/ServiceModel/Service"); Uri baseAddress1 = new Uri("http://localhost:8080/ServiceModel/Service1"); ServiceHost selfHost = new ServiceHost(typeof(TestService)); selfHost.AddServiceEndpoint(typeof(IService1), new WSHttpBinding(), baseAddress); selfHost.AddServiceEndpoint(typeof(IService2), new WSHttpBinding(), baseAddress1); ServiceMetadataBehavior smb = new ServiceMetadataBehavior(); smb.HttpGetEnabled = true; selfHost.Description.Behaviors.Add(smb); selfHost.Open(); Console.WriteLine("The service is ready."); Console.WriteLine("Press <ENTER> to terminate service."); Console.WriteLine(); Console.ReadLine(); selfHost.Close(); I'm getting a run time error as: The HttpGetEnabled property of ServiceMetadataBehavior is set to true and the HttpGetUrl property is a relative address, but there is no http base address. Either supply an http base address or set HttpGetUrl to an absolute address. What shall i do about it? Do I realy need two separate endpoints? Thanks.

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• When do instance variables get initialized and values assigned?

  - by AKh

  When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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• Using C++, how to call a base class method from a derived class method and apply this to an object passed as an argument?

  - by Chris

  I can't figure out how to call a base class method from a derived class method but concurrently applying this method call at an object passed as argument. What I mean is this: class Animal { virtual void eat(Animal& to_be_eaten) = 0; }; class Carnivores: public Animal { virtual void eat(Animal& to_be_eaten) { /*implementation here*/} }; class Wolf : public Carnivores { virtual void eat(Animal& to_be_eaten) { /*call eat method(of Base class) of Base to_be_eaten here*/ } } I thought of something like this dynamic_cast<Carnivores&>(to_be_eaten).eat(*this) //and got a segmentation fault Is there any way for this to be done? Thank you! New edit:: Updated the code

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• AS3 Memory management when instantiating extended classes

  - by araid

  I'm developing an AS3 application which has some memory leaks I can't find, so I'd like to ask some newbie questions about memory management. Imagine I have a class named BaseClass, and some classes that extend this one, such as ClassA, ClassB, etc. I declare a variable: myBaseClass:BaseClass = new ClassA(); After a while, I use it to instantiate a new object: myBaseClass = new ClassB(); some time after myBaseClass = new ClassC(); and the same thing keeps happening every x millis, triggered by a timer. Is there any memory problem here? Are the unused instances correctly deleted by the garbage collector? Thanks!

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