interface not able to use functions from base classes??

[Todd VanderVeen]

I presume your intent is to have B inherit the implementation 
from A. There are two options.

If you control class A and its appropriate to declare the 
interface there, you can declare that A implements I and have B 
simply inherit it from A.

class A : I {
    int f(int x) { return x; }
}

interface I { int f(int x); }

class B : A { }

void main() {
    writeln(new B().f(7));
}

If you only intend to introduce the interface on B, you still 
need to provide an implementation for I, either voluntarily 
overriding A or providing an alternate implementation to the 
virtual interface. To do the former, you can do the following:

class A {
    int f(int x) { return x; }
}

interface I { int f(int x); }

class B : A, I {
    override int f(int x) { return super.f(x); }
}

void main() {
    writeln(new B().f(7));
}




On Wednesday, 25 December 2013 at 07:40:03 UTC, Øivind wrote:
> Why doesn't this work:
>
> ----
>
> class A {
> 	int f(int x) {
> 		return x;
> 	}
> }
>
> interface I {
> 	int f(int x);
> }
>
> class B : A, I {
> 	
> }
>
> void main() {}
>
> ----
>
> I get the following error with DMD 2.064.2:
>
> /d122/f338.d(11): Error: class f338.B interface function 'int 
> f(int x)' is not implemented