virtual method pointer

[Jacob Carlborg]

On 2012-05-03 20:46, Gor Gyolchanyan wrote:
> I need to get a pointer to a virtual method, which is in turn a
> function pointer, being set by virtual method binding.
> Can anyone, please, tell me how to get it? Taking the delegate of the
> method won't do, because I need it to behave exactly as a virtual
> method call, except I pass the "this" explicitly.
> I need this in an event handling mechanism I'm making. You derive from
> the Sink class, passing your static type to the constructor, which
> scans your virtual methods, that conform to specific requirements and
> extracts them into an array, which later uses to dispatch the incoming
> events.
> It will feel much like a run-time virtual template method.

You can use two delegates:

class Foo
{
     void bar ()
     {
         writeln("Foo");
     }

     void delegate () resolveVirtualCall ()
     {
         return &bar;
     }

     static void forwardVirtualCall (Foo object)
     {
         void delegate () delegate () dg;
         dg.ptr = cast(void*) object;
         dg.funcptr = &resolveVirtualCall;
         dg()();
     }
}

class Bar : Foo
{
     void bar ()
     {
         writeln("Bar");
     }
}

void main()
{
     Foo b = new Bar;
     Foo.forwardVirtualCall(b);
}

Will print "Bar". If "resolveVirtualCall" is not used and "bar" is used 
directly instead, it will print "Foo".

-- 
/Jacob Carlborg