Re: I wish c++ did interfaces better.

From:

"Chris Becke" <chris.becke@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 6 Aug 2008 12:05:08 +0200

Message-ID:

<1218018642.7766@vasbyt.isdsl.net>

You know.
That works.
Im sure I tried virtual inheritance before and it did not work.
Perhaps it collapsed because the compiler i tried with (VC++ 8) doesn't =
implement virtual base classes correctly, or perhaps there is something =
fundamental that goes wrong when one tries to mix in overridden and =
inherited methods.

"kwikius" <andy@servocomm.freeserve.co.uk> wrote in message =
news:48996a8a_1@mk-nntp-2.news.uk.tiscali.com...

Chris Becke wrote:

Given an interface (in the c++ sense, nothing more than a struct =

containing pure virtual methods)

<...>

That of course never never never works. Why not?
So what that Ive introduced another method0()=0 ?
Why can't it figure out it already has an implementation
for that method that I'd really like to allow it to use?

  struct Iv1 {
      virtual void method0()=0;
  };

//And a class that implements the interface

  class Iv1Impl : public virtual Iv1 {
    virtual void method0(){}
  };

//Its not unreasonable to create a version 2 interface

  struct Iv2 : virtual Iv1 {
    virtual void method1()=0;};

//One might *try* to create an implementation class like this

  class Iv2Impl : public Iv2, Iv1Impl {
    virtual void method1(){} // implement Iv2 method
  };

int main()
{
  Iv2Impl x;
}

regards
Andy Little