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• C2664 when casting child class to templated parent class

  - by DC

  I have a parent class which is templated, and a child class which implements it. template< typename T1, typename T2> class ParentClass{ . . . }; class ChildClass : public ParentClass<MyT1, MyT2> { . . . }; And I want to have a pointer which I can use polymorphically: ParentClass<T1, T2>* ptr; ptr = static_cast<ParentClass<MyT1, MyT2>* >(new ChildClass() ); No matter how I cast it, I always get a C2664 which has the same expression: error C2664: cannot convert parameter 1 from 'ParentClass< T1,T2 *' to 'ParentClass< T1,T2 *' Is it not possible to cast pointer types between inherited types if the parent is templated, even if the types specified in the templates are the same?

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• StructureMap - Injecting a dependency into a base class?

  - by David

  In my domain I have a handful of "processor" classes which hold the bulk of the business logic. Using StructureMap with default conventions, I inject repositories into those classes for their various IO (databases, file system, etc.). For example: public interface IHelloWorldProcessor { string HelloWorld(); } public class HelloWorldProcessor : IHelloWorldProcessor { private IDBRepository _dbRepository; public HelloWorldProcessor(IDBRepository dbRepository) { _dbRepository = dbrepository; } public string HelloWorld(){ return _dbRepository.GetHelloWorld(); } } Now, there are some repositories that I'd like to be available to all processors, so I made a base class like this: public class BaseProcessor { protected ICommonRepository _commonRepository; public BaseProcessor(ICommonRepository commonRepository) { _commonRepository = commonRepository; } } But when my other processors inherit from it, I get a compiler error on each one saying that there's no constructor for BaseProcessor which takes zero arguments. Is there a way to do what I'm trying to do here? That is, to have common dependencies injected into a base class that my other classes can use without having to write the injections into each one?

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• Why am I getting this error when overriding an inherited method?

  - by Sergio Tapia

  Here's my parent class: public abstract class BaseFile { public string Name { get; set; } public string FileType { get; set; } public long Size { get; set; } public DateTime CreationDate { get; set; } public DateTime ModificationDate { get; set; } public abstract void GetFileInformation(); public abstract void GetThumbnail(); } And here's the class that's inheriting it: public class Picture:BaseFile { public override void GetFileInformation(string filePath) { FileInfo fileInformation = new FileInfo(filePath); if (fileInformation.Exists) { Name = fileInformation.Name; FileType = fileInformation.Extension; Size = fileInformation.Length; CreationDate = fileInformation.CreationTime; ModificationDate = fileInformation.LastWriteTime; } } public override void GetThumbnail() { } } I thought when a method was overridden, I could do what I wanted with it. Any help please? :)

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• EF 4.0 Code only assocation from abstract to derived

  - by Jeroen

  Using EF 4.0 Code only i want to make an assocation between an abstract and normal class. I have class 'Item', 'ContentBase' and 'Test'. 'ContentBase' is abstract and 'Test' derives from it. 'ContentBase' has a property 'Item' that links to an instance of 'Item'. So that 'Test.Item' or any class that derives from 'ContentBase' has an 'Item' navigation property. In my DB every record for Test has a matching record for Item. public class Item { public int Id { get; set;} } public abstract class ContentBase { public int ContentId { get; set;} public int Id { get; set;} public Item Item { get; set;} } public class Test : ContentBase { public string Name { get; set;} } now some init code public void SomeInitFunction() { var itemConfig = new EntityConfiguration<Item>(); itemConfig.HasKey(p => p.Id); itemConfig.Property(p => p.Id).IsIdentity(); this.ContextBuilder.Configurations.Add(itemConfig); var testConfig = new EntityConfiguration<Test>(); testConfig.HasKey(p => p.ContentId); testConfig.Property(p => p.ContentId).IsIdentity(); // the problem testConfig.Relationship(p => p.Item).HasConstraint((p, q) => p.Id == q.Id); this.ContextBuilder.Configurations.Add(testConfig); } This gives an error: A key is registered for the derived type 'Test'. Keys must be registered for the root type 'ContentBase'. anyway i try i get an error. What am i a doing wrong?

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• Nhibernate - getting single column from other table

  - by Muhammad Akhtar

  I have following tables Employee: ID,CompanyID,Name //CompanyID is foriegn key of Company Table Company: CompanyID, Name I want to map this to the following class: public class Employee { public virtual Int ID { get; set; } public virtual Int CompanyID { get; set; } public virtual string Name { get; set; } public virtual string CompanyName { get; set; } protected Employee() { } } here is my xml class <class name="Employee" table="Employee" lazy="true"> <id name="Id" type="Int32" column="Id"> <generator class="native" /> </id> <property name="CompanyID" column="CompanyID" type="Int32" not-null="false"/> <property name="Name" column="Name" type="String" length="100" not-null="false"/> What I need to add in xml class to map CompanyName in my result? here is my code... public ArrayList getTest() { ISession session = NHibernateHelper.GetCurrentSession(); string query = "select Employee.*,(Company.Name)CompanyName from Employee inner join Employee on Employee.CompanyID = Company.CompanyID"; ArrayList document = (ArrayList)session.CreateSQLQuery(query, "Employee", typeof(Document)).List(); return document; } but in the returned result, I am getting CompanyName is null is result set and other columns are fine. Note:In DB, tables don't physical relation Please suggest my solution ------ Thanks

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• Inheriting the main method

  - by Eric

  I want to define a base class that defines a main method that instantiates the class, and runs a method. There are a couple of problems though. Here is the base class: public abstract class Strategy { abstract void execute(SoccerRobot robot); public static void main(String args) { Strategy s = new /*Not sure what to put here*/(); s.execute(new SoccerRobot()) } } And here is an example derived class: public class UselessStrategy { void execute(SoccerRobot robot) { System.out.println("I'm useless") } } It defines a simple execute method, which should be called in a main method upon usage as a the main application. However, in order to do so, I need to instantiate the derived class from within the base class's main method. Which doesn't seem to be possible. I'd rather not have to repeat the main method for every derived class, as it feels somewhat unnessary. Is there a right way of doing this?

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• Abstract base class puzzle

  - by 0x80

  In my class design I ran into the following problem: class MyData { int foo; }; class AbstraktA { public: virtual void A() = 0; }; class AbstraktB : public AbstraktA { public: virtual void B() = 0; }; template<class T> class ImplA : public AbstraktA { public: void A(){ cout << "ImplA A()"; } }; class ImplB : public ImplA<MyData>, public AbstraktB { public: void B(){ cout << "ImplB B()"; } }; void TestAbstrakt() { AbstraktB *b = (AbstraktB *) new ImplB; b->A(); b->B(); }; The problem with the code above is that the compiler will complain that AbstraktA::A() is not defined. Interface A is shared by multiple objects. But the implementation of A is dependent on the template argument. Interface B is the seen by the outside world, and needs to be abstrakt. The reason I would like this is that it would allow me to define object C like this: Define the interface C inheriting from abstrakt A. Define the implementation of C using a different datatype for template A. I hope I'm clear. Is there any way to do this, or do I need to rethink my design?

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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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• Interface(s) inheriting other interface(s) in WCF services.

  - by avance70

  In my solution there's a few WCF services, each of them implementing it's own callback interface. Let's say they are called: Subscribe1, with ISubscribe1 and ICallback1, etc. It happens there are a few methods shared among ICallbacks, so I made a following interface: interface ICallback { [OperationContract] CommonlyUsedMethod(); } and i inherited it in all: ICallback1 : ICallback, ICallback2 : ICallback, etc. And deleted the CommonlyUsedMethod() from all callback interfaces. Now, on the service-side code, everything compiles fine and services can start working as usual. But, when I updated the service references for the client, CommonlyUsedMethod() dissapeared from the reference.cs file (the ISubscribeCallback part), and could no longer be used to send data to back to the client.

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• Different return value of an overridden class

  - by Samer Afach

  I have a simple but confusing question here. Is it legal to have a different return value type for overridden methods than the abstact ones defined in the base class?? I did that and the compiler didn't complain... could someone please explain? class MyBaseClass { int value; public: virtual int getValue() = 0; }; class MyClass : public MyBaseClass { double value; public: virtual double getValue(); // here!!! return is double, not int }; double MyClass::getValue() { return this->value; } The compiler totally accepted something similar (MSVC und MinGW)... could anyone please exaplain to what extent this is legal?

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• SRP & "axis of change"?

  - by lance

  I'm reading Bob Martin's principles of OOD, specifically the SRP text, and I understand the spirit of what it's saying pretty well, but I don't quite understand a particular phrasing, from page 2 of the link (page 150 of the book): I paraphrase: It is important to separate these two responsibilities into separate classes because each responsibility is an axis of change. What exactly is meant here by "axis of change"?

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• Rails 3 Abstract Class vs Inherited Class

  - by R. Yanchuleff

  In my rails 3 model, I have two classes: Product, Service. I want both to be of type InventoryItem because I have another model called Store and Store has_many :InventoryItems This is what I'm trying to get to, but I'm not sure how to model this in my InventoryItem model and my Product and Service models. Should InventoryItem just be a parent class that Product and Service inherit from, or should InventoryItem be modeled as a class abstract of which Product and Service extend from. Thanks in advance for the advice!

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• C++ function overloading and dynamic binding compile problem

  - by Olorin

  #include <iostream> using namespace std; class A { public: virtual void foo(void) const { cout << "A::foo(void)" << endl; } virtual void foo(int i) const { cout << i << endl; } virtual ~A() {} }; class B : public A { public: void foo(int i) const { this->foo(); cout << i << endl; } }; class C : public B { public: void foo(void) const { cout << "C::foo(void)" << endl; } }; int main(int argc, char ** argv) { C test; test.foo(45); return 0; } The above code does not compile with: $>g++ test.cpp -o test.exe test.cpp: In member function 'virtual void B::foo(int) const': test.cpp:17: error: no matching function for call to 'B::foo() const' test.cpp:17: note: candidates are: virtual void B::foo(int) const test.cpp: In function 'int main(int, char**)': test.cpp:31: error: no matching function for call to 'C::foo(int)' test.cpp:23: note: candidates are: virtual void C::foo() const It compiles if method "foo(void)" is changed to "goo(void)". Why is this so? Is it possible to compile the code without changing the method name of "foo(void)"? Thanks.

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• Doing things with objects as if they were parents

  - by General Ackbar

  Sorry that this is probably a super noob question. But the following code give me an error saying that there are invalid arguments in my call of doStuffToLines(segments) shouldnt I be able to do this since I have my DimensionLineSegment inherits from Lines? private void doStuff() { List<DimensionLineSegment> segments = new List<DimensionLineSegment>(); doStuffToLines(segments); } private void doStuffToLines(List<Line> lines) { }

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• How can I reuse a base class function in a derived class

  - by Armen Ablak

  Let's say we have these four classes: BinaryTree, SplayTree (which is a sub-class of BinaryTree), BinaryNode and SplayNode (which is a sub-class of BinaryNode). In class BinaryTree I have 2 Find functions, like this bool Find(const T &) const; virtual Node<T> * Find(const T &, Node<T> *) const; and in SplayTree I would like to reuse the second one, because it works in the same way (for example) as in SplayTree, the only thing different is the return type, which is SplayNode. I thought it might be enough if I use this line in SplayTree.cpp using BinaryTree::Find; but it isn't. So, how can I do this?

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• PHP: Extending static member arrays

  - by tstenner

  I'm having the following scenario: class A { public static $arr=array(1,2); } class B extends A { public static $arr=array(3,4); } Is there any way to combine these 2 arrays so B::$arr is 1,2,3,4? I don't need to alter these arrays, but I can't declare them als const, as PHP doesn't allow const arrays.http://stackoverflow.com/questions/ask The PHP manual states, that I can only assign strings and constants, so parent::$arr + array(1,2) won't work, but I think it should be possible to do this.

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• Java method get the inheriting type

  - by DrDro

  I have several classes that extend C and I would need a method that accepts any argument of type C. But in this method I would like to know if I'm dealing with A or B. * public A extends C public B extends C public void goForIt(C c)() If I cast how can I retrieve the type in a clean way (I just read using getClass or instanceof is often not the best way). PS: Fell free to edit an explicit title. *Sorry but I can't type closing braces

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• C++ overloading virtual = operator

  - by taz

  Hello, here is the code for my question: class ICommon { public: virtual ICommon& operator=(const ICommon & p)const=0; }; class CSpecial : public ICommon { public: CSpecial& operator=(const CSpecial & cs) { //custom operations return *this; } }; CSpecial obj; Basically: I want the interface ICommon to force it's descendants to implement = operator but don't want to have any typecasts in the implementation. The compiler says "can't instantiate an abstract class. Any help/advice will be appreciated.

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• To OpenID or not to OpenID? Is it worth it?

  - by Eloff

  Does OpenID improve the user experience? Edit Not to detract from the other comments, but I got one really good reply below that outlined 3 advantages of OpenID in a rational bottom line kind of way. I've also heard some whisperings in other comments that you can get access to some details on the user through OpenID (name? email? what?) and that using that it might even be able to simplify the registration process by not needing to gather as much information. Things that definitely need to be gathered in a checkout process: Full name Email (I'm pretty sure I'll have to ask for these myself) Billing address Shipping address Credit card info There may be a few other things that are interesting from a marketing point of view, but I wouldn't ask the user to manually enter anything not absolutely required during the checkout process. So what's possible in this regard? /Edit (You may have noticed stackoverflow uses OpenID) It seems to me it is easier and faster for the user to simply enter a username and password in a signup form they have to go through anyway. I mean you don't avoid entering a username and password either with OpenID. But you avoid the confusion of choosing a OpenID provider, and the trip out to and back from and external site. With Microsoft making Live ID an OpenID provider (More Info), bringing on several hundred million additional accounts to those provided by Google, Yahoo, and others, this question is more important than ever. I have to require new customers to sign up during the checkout process, and it is absolutely critical that the experience be as easy and smooth as possible, every little bit harder it becomes translates into lost sales. No geek factor outweighs cold hard cash at the end of the day :) OpenID seems like a nice idea, but the implementation is of questionable value. What are the advantages of OpenID and is it really worth it in my scenario described above?

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• Why can't I *override* and *new* a Property (C#) at the same time?

  - by Tim Lovell-Smith

  According to this question it seems like you can do this for Methods. What I want to know is why it doesn't work when I try it with properties. public class Foo { public virtual object Value { get; set; } } public class Foo<T> : Foo { public override object Value { get { return base.Value; } set { base.Value = (T)value; //inject type-checking on sets } } public new T Value { get { return (T)base.Value; } set { base.Value = value; } } } Error message from C# 4.0 RC1 Error 1 The type 'ClassLibrary1.Foo' already contains a definition for 'Value' ClassLibrary1\Class1.cs 31 22 ClassLibrary1

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• How to find out the subclass from the base class object

  - by Vaishak Suresh

  Is there a way to find out the derived class's name from a base class object? ex: class A{ .... } class B extends A{ ... } class c extends A{ ... } now if a method returns an object of A, can I find out if it is of type B or C?

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• How to determine which inheriting class is using an abstract class's methods.

  - by Kin

  In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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• how to achieve this single line css format....

  - by metal-gear-solid

  I tried many formats but this is best to find classes and IDs easily without using "Find". but it is good if width of editor is wide. I use this tool to format my css in single line http://www.newmediacampaigns.com/files/posts/css-formatting/clean.php #wrapper {width:800px; margin:0 auto;} #header {height:100px; position:relative;} #feature .post {width:490px; float:left;} #feature .link {width:195px; display:inline; margin:0 10px 0 0;float:right;border-bottom:1px solid red} #footer {clear:both; font-size:93%; float:none;} I need like this. see selector #feature .link i need if any selector has more than 3 properties then it should go at next line like in this example.because i work in cms where width of textbox where i write cssis not much wide. Is there any tool/software can format CSS like this. or after getting single line format can we this formatting for big lines. in automated way #wrapper {width:800px; margin:0 auto;} #header {height:100px; position:relative;} #feature .post {width:490px; float:left;} #feature .link {width:195px; display:inline; margin:0 10px 0 0; float:right;bottom:1px solid red} #footer {clear:both; font-size:93%; float:none;}

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• Seam @Factory in abstract base class?

  - by Shadowman

  I've got a series of web actions I'm implementing in Seam to perform create, read, update, etc. operations. For my read/update/delete actions, I'd like to have individual action classes that all extend an abstract base class. I'd like to put the @Factory method in the abstract base class to retrieve the item that is to be acted upon. For example, I have this as the base class: public abstract class BaseAction { @In(required=false)@Out(required=false) private MyItem item=null; public MyItem getItem(){...} public void setItem(...){...} @Factory("item") public void initItem(){...} } My subclasses would extend BaseAction, so that I don't have to repeat the logic to load the item that is to be viewed, deleted, updated, etc. However, when I start my application, Seam throws errors saying I have declared multiple @Factory's for the same object. Is there any way around this? Is there any way to provide the @Factory in the base class without encoutnering these errors?

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