From: "Gray, Jeff" <jeff.gray@...>
Date: 2002-09-21T09:34:21+09:00
Subject: RE: Creating a method given a block

> From: Hal E. Fulton [mailto:hal9000@hypermetrics.com]
>
> Suppose I have a method 'build' to which I am passing
> (among other things) a Symbol and a block.
> 
> The build method will define a method of the given
> name and the block will in effect be the "body"
> of that block.
> 
> I've been messing with Procs trying to get this to
> work. Just can't figure it out.
> 

Here's my quick take (without your extra args):

--
class Extendable
  @@dispatch_table = Hash.new
  def build(name, &block)
    @@dispatch_table[name] = block
    Extendable.class_eval <<-EVAL
      def #{name.to_s}(*args)
        @@dispatch_table[:#{name}].call(*args)
      end
EVAL
  end
end

a = Extendable.new
a.build(:foo) { |str| puts "foo:#{str}" }
a.build(:noo) { |str1, str2| puts "noo:#{str1};#{str2}" }

a.foo("bar")           #->  "foo:bar"
a.noo("baz", "blah")   #->  "noo:baz;blah"
--

If you're 'eval'-averse, you could replace the class_eval with a
method_missing trap instead.

 - jeff