Defining method_missing and respond_to? in one fell swoop

match_method.rb

# Do you ever define #method_missing and forget #respond_to? I sure
# do.  It would be nice if we could do them both at the same time.

module MatchMethodMacros
  def match_method(matcher, &method_body) 
    mod = Module.new do
      define_method(:method_missing) do |method_name, *args, &blk|
        if matcher === method_name.to_s
          instance_exec(method_name, *args, blk, &method_body)
        else
          super(method_name, *args)
        end
      end

      define_method(:respond_to_missing?) do |method_name, include_private|
        # Even though this is in the #respond_to_missing? hook we
        # still need to call 'super' in case there are other included
        # modules which also define #respond_to_missing?
        (matcher === method_name) || super(method_name, include_private)
      end
    end
    include mod
  end
end

class Foo
  extend MatchMethodMacros

  match_method(/\Amake_me_a_/) do |name, *args|
    food = /\Amake_me_a_(.*)$/.match(name.to_s)[1]
    "Make your own damn #{food}"
  end

  match_method(/\Asudo_make_me_a/) do |name, *args|
    block = args.pop if args.last.is_a? Proc
    suffix = " with #{block.call}" if block
    food = /\Asudo_make_me_a_(.*)$/.match(name.to_s)[1]
    "Coming right up, one #{food}#{suffix}"
  end

  def method_missing(name, *args)
    # match_method uses modules, so we can use super to delegate to
    # the generated #method_missing definitions.
    super
  rescue NoMethodError
    "We don't do that kind of thing here"
  end
end

foo = Foo.new

puts foo.respond_to?(:fix_me_a_sandwich) # => false
puts foo.respond_to?(:make_me_a_sandwich) # => true
puts foo.respond_to?(:sudo_make_me_a_sandwich) # => true

puts foo.fix_me_a_sandwich # => "We don't do that kind of thing here"
puts foo.make_me_a_sandwich # => "Make your own damn sandwich"
puts foo.sudo_make_me_a_sandwich # => "Coming right up, one sandwich"
puts foo.sudo_make_me_a_sandwich { 'love' } # => "Coming right up, one sandwich with love"