D1/D2: How to check if a method has been overridden

[Max Samukha]

On 09/08/2010 12:33 AM, klickverbot wrote:

>
> Well, I guess I should have wrote the following instead:
>

You can avoid messing with vtable:

class A {
     void foo( float a ) {}
     void foo( int a ) {}

     // hack to get the static address of an overload
     private static Fn funcAddr(Fn, alias fn)() {
         return cast(Fn)&fn;
     }

     private bool isOverriden(Dg, alias fn)() {
         Dg dg = &foo;
         // check if the static and dynamic addresses match
         return dg.funcptr != funcAddr!(typeof(dg.funcptr), fn);
     }

     final void bar() {

         writefln("%:", this.classinfo);
         if (isOverriden!(void delegate(float), foo))
             writefln("  foo(float) is overriden");

         if (isOverriden!(void delegate(int), foo))
             writefln("  foo(int) is overriden");
     }
}

class B : A {
    alias A.foo foo;
    override void foo( float a ) {}
}

class C : A {
    alias A.foo foo;
    override void foo( int a ) {}
}

class D : B {
    alias B.foo foo;
    override void foo( int a ) {}
}

void main()
{
     auto a = new A;
     a.bar();

     a = new B;
     a.bar();

     a = new C;
     a.bar();

     a = new D;
     a.bar();
}

No guarantees at all as you never know whether you are dealing with a 
bug or feature.