From: Rick DeNatale <rick.denatale@...>
Date: 2007-10-26T06:36:28+09:00
Subject: Re: Need help understanding metaclassing

On 10/25/07, Chris Czub <chris.czub@gmail.com> wrote:
> Daniel Waite wrote:
> > That's the same code as above. Still doesn't work though. =)
>
> Nope, it's c.eat instead of cs.eat... works for me! :)
> --

Right.

This is a slightly different case that I had described.

In my example

class Foo
    metaclass.instance_eval {define_method(:bar) {"bar"}}
end

It's Foo's singleton/metaclass which get the define_method call.

Whereas

this new case is equivalent to

c = Creature.new
c.singleton.instance_eval {define_method(:eat) {puts "You eat"}}

So in my case, the class Foo ends up with a new method, i.e. a class
method since Foo is a class,
but c ends up with a new singleton (instance) method.

And if you did

c.class.instance_eval{define_method(:walk) {puts "You walk"}}

An instance method would be created which would be invocable for all
instances of Creature, because this is the same as

Creature.instance)_eval ...

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/