From: Lionel Thiry <lthiryidontwantspam@...>
Date: 2005-04-06T00:09:43+09:00
Subject: Re: [EVALUATION] - E03b - The Ruby Object Model

Ilias Lazaridis a �crit :
 > [snip]
> I cannot access any of the metaclasses
> 
> the same in the documentation: no metaclasses
> 
> -
> 
> Any suggestions / clarifications?
> 
> .
> 

Most of the time, everything goes in ruby as if there weren't any kind of 
metaclasses. For exemple, you cannot explicitely create your own metaclasses:

class MyMetaClass < Class
end

It raises the exception:
metaclass.rb:1: can't make subclass of Class (TypeError)

Instead of thinking in metaclasses, everything goes as if you were asked to 
think in terms of singleton methods. (this has nothing to do with the Singleton 
Pattern)

class MyClass
  def method
   puts "normal method"
  end
  def self.method
   puts "singleton method or metaclass method?"
  end
end

MyClass.new.method
# => Normal method

MyClass.method
# => singleton method or metaclass method?

p MyClass.singleton_methods
# => ["method"]

class Foo
  def test
   puts "instance method"
  end
end

foo = Foo.new

foo.test
# => instance method

class << foo
  def test
   puts "singleton method"
  end
end

# singleton methods have precedence over instance method
foo.test
# => singleton method

p foo.singleton_methods
# => ["test"]

--
Lionel Thiry