From: Collins <ccw.in.nc@...>
Date: 2010-08-27T03:40:06+09:00
Subject: Re: Idiom or method for determining where in the class hierarchy an object fits

On Aug 26, 2:30 pm, Mike Stok <m...@stok.ca> wrote:
> On Aug 26, 2010, at 2:15 PM, Collins wrote:
>
>
>
>
>
> > I have a class hierachy that looks like this
>
> > class A
> > ...
> > end
>
> > class B < A
> > ...
> > end
>
> > class C < A
> > ...
> > end
>
> > class D < B
> > ...
> > end
>
> > class E < C
> > ...
> > end
>
> > class F < B
> > ...
> > end
>
> > Now class B has a method that expects either members of class D or E
> > or Fas a parameter but needs to do something different based upon the
> > whether the parameter is a subclass of B or a subclass of C.
> > I could check to see if it was D or F as opposed to B but that would
> > mean when I added class G<B...end I'd have to go back and touch B.
> > Is there a way to ask an object if it is descended from a particular
> > class?  I suppose I could add a method to B and test for the presence
> > of that method in the parameter objects but that feels ucky.
>
> >  Thanks
>
> >    Collins
>
> You could try kind_of? e.g.
>
>  >> o = F.new
>  => #<F:0x00000100a74a30>
>  >> o.kind_of?(A)
>  => true
>  >> o.kind_of?(B)
>  => true
>  >> o.kind_of?(C)
>  => false
>
> etc.
>
> Hope this helps,
>
> Mike
>
> --
>
> Mike Stok <m...@stok.ca>http://www.stok.ca/~mike/
>
> The "`Stok' disclaimers" apply.

Thank you!  I was only aware of instance_of?  This is exactly what I
was hoping to find...

  Thanks again

    Collins