From: Tim Pease <tim.pease@...>
Date: 2007-01-13T05:54:43+09:00
Subject: Re: Rake, Hoe, Meta-Programming, and Warnings (oh my!)

On 1/12/07, Mike Harris <GENIE@prodigy.net> wrote:
> I understand that this isn't identical to what you're doing, but it
> demonstrates how define_method won't cause a warning.
>
> class Foo
>   define_method(:bar) do
>     puts "bar"
>   end
>   def cat
>     puts "cat"
>   end
> end
>
> Foo.new.bar
> Foo.new.cat
>
> class Foo
>   define_method(:bar) do
>     puts "bar2"
>   end
>   def cat
>     puts "cat2"
>   end
> end
>
> Foo.new.bar
> Foo.new.cat
>
>  >ruby -w foo.rb
> bar
> cat
> foo.rb:17: warning: method redefined; discarding old cat
> bar2
> cat2
>
>
>

There is going to be a performance hit with define_method.  Since the
method body is a block, each time it is called a Binding to the
instance will have to be created in which the block will be run.

$ cat a.rb

require 'benchmark'

class Object
  def method() end
  define_method(:method1) {}
end

this_many = 1_000_000
::Benchmark.bm(10) do |bm|
  bm.report('method     :') {this_many.times {method()}}
  bm.report('method1    :') {this_many.times {method1()}}
end


$ ruby a.rb
                user     system      total        real
method     :  0.400000   0.000000   0.400000 (  0.400000)
method1    :  1.272000   0.000000   1.272000 (  1.282000)



It is a factor of 3 slower   :(

Blessings,
TwP