A large executable list of methods of define singleton methods in ruby

singleton_methods.rb

##############################################
# Different ways to define singleton methods #
##############################################

# Being able to reference external instance variables when creating a method 
# enables useful meta-programming techniques in ruby. The styles which are
# capable of this will define methods that "Moof!" (like Clarus the Dogcow).

moof = "Moof!"

def test_singleton_method desc="#?"
  animal = 'dog'

  yield animal

  puts "#{desc}: \t#{animal.speak}"
end


#=============================================

test_singleton_method "#1" do |dog|
  def dog.speak
    defined?(moof)? moof : "Woof"
  end
end

test_singleton_method "#2" do |dog|
  dog.instance_eval do
    def speak
      defined?(moof)&&moof||"Woof"
    end
  end
end

test_singleton_method "#3" do |dog|
  class << dog
    def speak
      defined?(moof)? moof : "Woof"
    end
  end
end

test_singleton_method "#4" do |dog|
  class << dog
    define_method(:speak) do
      defined?(moof)? moof : "Woof"
    end
  end
end

test_singleton_method "#5" do |dog|
  class << dog
    define_method(:speak, lambda { defined?(moof)? moof : "Woof" })
  end
end

test_singleton_method "#6" do |dog|
  module SpeakableDog
    def speak
      defined?(moof)? moof : "Woof"
    end
  end

  class << dog
    include SpeakableDog
  end
end

test_singleton_method "#7" do |dog|
  module SpeakableDog
    def speak
      defined?(moof)? moof : "Woof"
    end
  end

  dog.extend SpeakableDog
end

test_singleton_method "#8" do |dog|
  klass = class << dog; self; end
  klass.send :define_method, :speak do
    defined?(moof)? moof : "Woof"
  end
end

#================ Ruby 1.9.2 ====================

test_singleton_method "#9" do |dog|
  module SpeakableDog
    def speak
      defined?(moof)? moof : "Woof"
    end
  end

  dog.singleton_class.send(:include, SpeakableDog)
end

test_singleton_method "#10" do |dog|
  dog.singleton_class.class_eval do
    def speak
      defined?(moof)? moof : "Woof"
    end
  end
end

test_singleton_method "#11" do |dog|
  dog.singleton_class.send(:define_method, :speak) do
    defined?(moof)? moof : "Woof"
  end
end

test_singleton_method "#12" do |dog|
  dog.define_singleton_method(:speak) do
    defined?(moof)? moof : "Woof"
  end
end

test_singleton_method "#13" do |dog|
  dog.singleton_class.send(:define_method, :speak, lambda { defined?(moof)? moof : "Woof" })
end