🚀 go-pugleaf

Steve Horsley wrote:
> 
> On Wed, 19 Jun 2002 23:12:14 +0100, "Coho (Richard Swain)"
> <vibron@krang.f9.co.uk> wrote:
> 
> >> almost need to create a new interface:
> >>
> >> interface ThingThatDoesIntf1AndIntf2 {
> >>     Intf1 getIntf1();
> >>     intf2 getIntf2();
> >> }
> >>
> >> Except that you can't even pass this object round to a method that
> >> expects to be given an Intf1 or an Intf2.
> >
> >But I don't see how using somekind of namespace resolution is
> >polymorphic either. i.e to specify which method to call you *have*
> >to specify the interface the method is on. IMHO getIntfN() does that
> >just as well as some kind of language trick.
> >
> Me neither. Perhaps the best approach is to use a convention like:
>     public void intf1_draw()...
>     public void intf2_draw()...
> but I don't think people are likely to adopt it.
> 
> >You are right about specifying a new interface, but I would hope that
> >practically all concrete classes are expressions of interfaces - to
> >which those two methods can be added.
> >
> >If a method takes a particular interface intf1 say you can always do
> >
> >theMethod( myclass.getIntf1() );
> >
> That's not too bad. Except that there's no way to get back from the
> Intf1 to the original myClass object. I'm not sure you should ever
> want to, but I still feel alienated by this somehow.
> 

You could do this if you really wanted to do.  What you'd have to do is
enhance all your interfaces with an extra method:

    Object getContainingObject();

and then implement it this way within the anonymous call:

    Intf1  getIntf1()
        {
        return new Intf1()
        {
            public void X()
            {
                intf1X();
            }
            public Object getContainingObject() {
                return <Name of Containing Class>.this;
            }
        };
    }

Admittedly not as easy as in a direct implementation, but it seems to work.

Wayne