Overriding methods declaration problems

**TurboTuring** · July 9th, 2010, 07:06 AM

Hello! I have recently joined this forum, so I don´t know if I am doing it correctly posting this thread here.

I am having problems with this:

I want develop an interface IB that extends an interface IA

Interface IA has a method :

void M(IC pIC );

and interface IB, has a method :

void M(ID pID);

Also happends that interface ID extends interface IC, so I want that interface's IB method M declaration overrides interface's IA method M declaration. Then when an Object implements interface IB, it will have to implement method "void M(ID pID);" but not the method "void M(IC pIC );".

My questions are:

This can be done?

If it can be done, how can I make it?

Thanks for helpping me, or for trying to help.

**aussiemcgr** · July 9th, 2010, 07:25 AM

I'll attempt to help you out more in about an hour or so when I can get back on a computer. For the time being, I have one question to make sense of this for me. What is the purpose and/or benefit for several interfaces implementing each other in your context?

**TurboTuring** · July 9th, 2010, 07:47 AM

In fact, IA and IB are interfaces of view controllers, and IC and ID ar interfaces of views.

IA is implemented by an abstract class that represents a general kind of view controller, and IB is implemented by a class that represents a concrete view controller.

IC is implemented by an abstract class that represents a general kind of view, and IB is implemented by a class that represents a concrete view.

The method M in fact is a method that sets one attribute of the view controller which implements it. It sets the "view" attribute for that controller, and depending on the controller class, that attribute may be a class of kind IC or of kind ID. That way, allowing to the implementers of IB (concrete controllers) execute void M(IC pIC); may be wrong, because IC its implemented by a (general view).

I don´t know if I am explaining it correctly.

Any more question you want to ask, just tell me.

Thanks.

**Norm** · July 9th, 2010, 08:11 AM

This can be done?

What happens when you write a simple program to test it?
The compiler will tell you very quickly if it "can be done". No sense waiting for someone at a forum to try it.

**TurboTuring** · July 9th, 2010, 08:33 AM

Sorry, I forgot to post what the compiler told me. If a program it, without using generics, it tells me that I have to implement both methods :

void M(IC pIC);
void M(ID pID);

in the class that implements IB.

I also tried :

public interface IA {
   <IZ extends IC>void method(IZ pIZ);
}
 
public interface IB extends IA {
    <IZ extends IC,ID> void method(IZ pIZ);
 
}

An also tells me to implement both methods, but when I implement them, it says me that there is an error because both methods have the same erasure. So I tried to change the order of extends IC,ID to extends ID,IC, but it tells me to implement both. Finally I tried :

public interface IA<IZ extends IC> {
   <IZ extends IC>void method(IZ pIZ);
}
 
public interface IB<IZ extends ID,IC> extends IA<IZ> {
    <IZ extends ID,IC> void method(IZ pIZ);
}

An again tells me the same. An if then I change extends ID,IC to extends IC,ID, having the same erasure, I get overriden the method but with void M(IC pIC ); and not with void M(ID pID);

I am beggining to think that it can´t be done.

Thanks.

**Norm** · July 9th, 2010, 08:34 AM

The compile would tell you if what you are doing is wrong.

**cosecant** · July 9th, 2010, 11:23 AM

IB's void M doesn't really override IA's void M because IB's method restricts the arguments to only ID's so ID is different from IC. Therefore void M would be an overloaded method.

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