From: Kirk Haines <khaines@...>
Date: 2005-08-02T06:47:55+09:00
Subject: Selective mixins; who can improve on this?

So, on #ruby-lang an hour ago, Daniel Berger asked for ideas to make some 
non-working code of his work.  He's trying to come up with a way to 
selectively mixin methods from a module into a class.

After some tinkering, I came up with this working, but ugly and definitely 
improveable code to do it:

class Module
  def use(mod, *methods)
    c = Class.new
    # Make a singleton that mixes everything in, so that we can cherrypick.
    eval("class << c; include #{mod}; end")
 
    methods.each do |m|
      # There has to be a more elegant way to do this.
      m_sym = m.to_sym
      mc_sym = m.to_s.upcase.to_sym
      um = c.method(m_sym)
      self.const_set(mc_sym,um)
      self.class_eval("def #{m.to_s}; #{mc_sym.to_s}.call; end")
    end
  end
end
 
 
module Foo
  def a; 'abc'; end
  def z; 'xyz'; end
end
 
class Bing
  use(Foo, :a, 'z')
end
 
x = Bing.new
p x.a
p x.z


There has to be a more elegant way to do this.  What is it?


Kirk Haines