From: Daniel DeLorme <dan-ml@...42.com>
Date: 2006-07-25T23:16:54+09:00
Subject: Re: I'll have the duck!

dblack@wobblini.net wrote:
> The problem is that "duck typing" is already "taken" :-)

*sigh*
And So, Faced With Insurmountable Semantic Opposition And A
Total Lack Of Suggestions, I Was Faced With The Lonely Task
Of Renaming My Proof-Of-Concept Module, Carefully Removing
Any Offending Reference To The Word "Duck":


module DependentMethods
   @@dependent_methods = Hash.new{ |h,k| h[k] = {} }

   def depending_on(*requisites, &block)
     o = self.is_a?(Class) ? self : self.class
     requisites.unshift(o)

     before = o.instance_methods
     o.class_eval(&block)
     after = o.instance_methods

     for methodname in (after - before)
       methodname = methodname.to_sym
       @@dependent_methods[methodname][requisites] = o.instance_method(methodname)
       o.send(:remove_method, methodname)
     end
   end

   def dependent_method(methodname)
     @@dependent_methods[methodname.to_sym].each do |requisites, m|
       if self.kind_of?(requisites[0])
         if requisites[1..-1].all?{ |r| self.respond_to?(r) }
           return m
         end
       end
     end
     return nil
   end

   def method_missing(methodname, *args, &block)
     if m = dependent_method(methodname)
       m.bind(self).call(*args, &block)
     else
       super
     end
   end
end
Object.module_eval{ include DependentMethods }


depending_on :quack do
   def quack_loudly
     ([quack.upcase]*(1+rand(3))).join
   end
end

class Anatidae
   def quack
     "quack!"
   end
end

d = Anatidae.new
puts d.quack_loudly #=> "QUACK!"