dynamically defined methods in ruby

I've been playing around with dynamically creating methods today and it's mighty cool stuff. here's a very contrived demo class:

class Demo
  METHODS=["one","two","three","four"]
  METHODS.each { |name|
    define_method("method_#{name}") do 
      |arg|
      puts "this method is named method_\"#{name}\" and you gave me the arg \"#{arg}\""
    end
  }
end

and me using it in irb

irb> demo = Demo.new
=> #<Demo:0xb7be8900>
irb> demo.method_one("this is an arg")
this method is named "method_one" and you gave me the arg "this is an arg"
=> nil
irb> demo.method_two("this is an arg")
this method is named "method_two" and you gave me the arg "this is an arg"
=> nil
irb> demo.method_four("this is another arg")
this method is named "method_four" and you gave me the arg "this is another arg"
=> nil