Re: new virtual functions

From: headware (dkland_at_cox.net)
Date: 12/20/04 

Date: 20 Dec 2004 09:51:00 -0800

I see. You're right, that doesn't seem like something you would use too
often, but that does solve the problem you mentioned. Thanks for the
reply.

Dave

Jon wrote:
> headware <dkland@cox.net> wrote:
>
> <snip>
>
> > It makes sense to me that cRef.f() prints out "D.f()", that is
basic
> > polymorphism. What doesn't make that much sense to me is why
aRef.f()
> > prints out "B.f()". Why should a reference of type A pointing to an
> > object of type D call B.f()? I realize that it has to do with the
fact
> > that f() is declared as new virtual in C. What I don't understand
is
> > why this is the correct behavior. Why would you even want to do
> > something like this? How could this be used?
>
> B.f() overrides A.f(), which is basically what you're calling when
you
> use aRef.f(). C.f() and D.f() are completely separate methods to
A.f()
> and B.f() as far as the compiler is concerned.
>
> As for why/when you'd want to use it - very rarely, basically. The
> usual situation would be if you've got a library class and a class
> you've derived from it. You've put in a method called Foo(), and then

> in the next version of the library that class gains a method called
> Foo() as well, which might be meant to do something completely
> different. You don't want to override the library class's Foo()
method,
> because then the library class would be expecting it to do one thing
> and it would actually do another, but you still want your code which
> uses your Foo() method to compile and run properly.
>
> --
> Jon Skeet - <skeet@pobox.com>
> http://www.pobox.com/~skeet
> If replying to the group, please do not mail me too

Relevant Pages

  • Re: a case for multiple inheritance
    ... and overrides the write functions to change ... the compiler would optimize it so that the double function call would be ... private new void Foo ... The cast not much ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: a case for multiple inheritance
    ... the compiler would optimize it so that the double function call would be ... private new void Foo ... The cast not much ... This means that if method A1 overrides ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: a case for multiple inheritance
    ... and overrides the write functions to change ... the compiler would optimize it so that the double function call would be ... private new void Foo ... The cast not much ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: new virtual functions
    ... B.foverrides A.f, which is basically what you're calling when you ... and B.fas far as the compiler is concerned. ... Foo() as well, which might be meant to do something completely ... because then the library class would be expecting it to do one thing ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: Sacla loop: a new loop implementation
    ... >> Finally, once the foo macro receives its argument, then based on what ... >> depending on how the macro is defined. ... transformations and optimizations deep in the bowels of the compiler, ... > available at macroexpansion time. ...
    (comp.lang.lisp)
Loading