From: Daniel Schierbeck <daniel.schierbeck@...>
Date: 2005-10-18T23:51:58+09:00
Subject: Duck-typing

Tell me if this is stupid. I'm sure there's a simpler and faster way to 
do this, but I'm interested in knowing whether the idea itself is... 
well, stupid.

   class Object
     def quacks_like? (klass)
       klass.public_instance_methods.each do |method|
         return false unless respond_to? method
       end
       return true
     end
   end

   class A
     def foo; end
     def bar; end
   end

   class B
     def foo; end
   end

   if A.new.quacks_like? B
     puts "A quacks like B"
   else
     puts "A doesn't quack like B"
   end

   # => "A quacks like B"

   if B.new.quacks_like? A
     puts "B quacks like A"
   else
     puts "B doesn't quack like A"
   end

   # => "A doesn't quack like B"

Basically, when I call obj.quacks_like? Klass I ask if every public 
method defined in Klass is defined in obj as well.


Cheers,
Daniel