gistfile1.rb

class Object
  def metaclass
    class << self; self; end
  end
end

class Foo
  def self.hello
    puts "hello"
  end
end


class Bar < Foo
  def self.goodbye
    puts "goodbye"
  end
end

# In Ruby, classes are objects. Class methods are singleton methods of the 
# class object.

p Bar.object_id
# => 59030

p Bar.singleton_methods.sort
# => ["goodbye", "hello"]

# But they are not defined on the class object itself - they instance methods 
# of the classes eigenclass/metaclass

p Bar.metaclass.instance_methods.sort - Class.instance_methods
# => ["goodbye", "hello"]

# You can also define singleton methods on "regular" objects

s = "hello I'm a String"
class << s; def random_method; self.split("").sort_by{ rand }.join;end;end
p s.random_method
# => "tea'Smi nr o llgIh"

p s.singleton_methods
# => ["random_method"]

p s.metaclass.instance_methods.sort - String.instance_methods
# => ["random_method"]

# So this works just as with classes basically. Objects and classes have 
# metaclasses because they are both objects. The only difference is that
# classes can be inherited and so it is possible to reach into the superclasses
# metaclass

p Bar.superclass.metaclass.instance_methods.sort - Class.instance_methods
# => ["hello"]