From: Collins <ccw.in.nc@...>
Date: 2010-08-27T03:15:16+09:00
Subject: Idiom or method for determining where in the class hierarchy an object fits

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