Eigenclasses in Ruby

eigenclass.rb

# In Ruby everything is an object, including classes.
# That means class methods are instance methods of some object.
# But what object?

class Object
  def eigenclass 
    class << self
      self
    end 
  end 
end

class Foo
  def self.zzzz
    "Sleepy time time, all the time. - Cream, 1966"
  end
end

Foo.instance_methods.include?(:zzzz)            # => false
Foo.methods.include?(:zzzz)                     # => true
Foo.eigenclass.instance_methods.include?(:zzzz) # => true

# And now for something completely different

Foo.class                 # => Class
Foo.superclass            # => Object

Foo.eigenclass.class      # => Class
Foo.eigenclass.superclass # => #<Class:Object>

anon = Class.new

anon #=> #<Class:0x...>
anon.singleton_class #=> #<Class:#<Class:0x...>>

Foo = anon

anon #=> Foo
anon.singleton_class #=> #<Class:Foo>