Re: How to determine if a function is implemented

[Kenji Hara]

On Friday, 5 July 2013 at 01:27:06 UTC, JS wrote:
the code
http://dpaste.dzfl.pl/25bfeeb7

attempts to implement an interface. The current issue is that I 
need to determine if the user has added the member of the 
interface to the class or if the mixin needs to add it.


so the lines

class B : A
{
        A a;
        
        //void myfunc(float a, int b, string c) { };
        //@property int myvalue() { return 4; }
        mixin implementInterface!a;
}

The mixin adds the two commented functions above it which 
effectively implement the interface A in B. The problem is, I 
might want to manually specify one, e.g.,


class B : A
{
        A a;
        
        void myfunc(float a, int b, string c) { };
        //@property int myvalue() { return 4; }
        mixin implementInterface!a;
}

So the mixin needs to be aware and not add a method that is 
already implemented.
I need some way for the mixin to distinguish the two cases 
above. e.g., isImplemented!(myfunc(float, int, string)) or 
something like that.

It's completely unnecessary. A mixed-in function cannot override 
properly declared function that has same name in the mixed-in 
scope.


interface I { int foo(); }

mixin template Foo()
{
    override int foo() { return 1; }
}

class C1 : I {
    mixin Foo!();
}

class C2 : I
{
    int foo() { return 10; }
    mixin Foo!();
    // mixed-in foo is not stored in vtbl
}

void main()
{
    assert(new C1().foo() == 1);
    assert(new C2().foo() == 10);
}

Kenji Hara