what pattern or policy to use.

This is the problem,

the class diagram is


C Impl

IC EC SImpl HImpl

Where IC and EC are derived from C(Abstract) and SImpl and HImple are
derived from Impl(Abstract). C keeps a pointer to Impl.

If I have to invoke a function of SImpl then I can declare a virtual
function in Impl and do it, straight forward.
Question is, if I have to write a function which only makes sense for
SImpl and not for HImpl and this function is to be called from IC.
Then how should I do it using patterns or policy.
Any suggestion....
Thanks

Here's my 2 cents worth:

class C {
private Impl impl;
protected setImpl(Impl impl) {
this.impl = impl;
}
public someMethod() {
Object ref = impl.anImplMethod();
....
}
}

public class IC extends C {
C(Impl impl) {
super();
setImpl(impl);
}
public void someMethod(){
assert impl instanceof SImpl;
Object ref = ((SImpl) impl).aSImplMethod();
....
}
}

Cheers

sanjrd@yahoo.com (sanjiv) wrote in message news:<8ad413cf.0411021420.7a33d889@posting.google.com>...
> This is the problem,
>
> the class diagram is
>
>
> C Impl
>
> IC EC SImpl HImpl
>
> Where IC and EC are derived from C(Abstract) and SImpl and HImple are
> derived from Impl(Abstract). C keeps a pointer to Impl.
>
> If I have to invoke a function of SImpl then I can declare a virtual
> function in Impl and do it, straight forward.
> Question is, if I have to write a function which only makes sense for
> SImpl and not for HImpl and this function is to be called from IC.
> Then how should I do it using patterns or policy.
> Any suggestion....
> Thanks