Overriding the behavior of a Mixin module by mixing in another module

Question

I want to be able to switch back and forth as the instance responds to the message. I want to do this by mixing in a module and then later moving in another module to override this behavior.

Example:

module Dog
  def speak
    puts "woof woof"
  end
end

module Cat
  def speak
    puts "meow"
  end
end

class Animal
end

Now I want to switch back and forth how the instance Animalresponds to the message speak:

animal = Animal.new

animal.extend(Cat)
animal.speak

animal.extend(Dog)
animal.speak

animal.extend(Cat)
animal.speak

animal.extend(Dog)
animal.speak

animal.extend(Cat)
animal.speak

I expect this code to output the following:

meow
woof woof
meow
woof woof
meow

Instead, it is output as follows:

meow
woof woof
woof woof
woof woof
woof woof

Any tips on how I can get this to work as expected?

Answer 1

I adapted the answer to your other question in the Adapter pattern in ruby: access to instance variables

module Dog
  def speak
    puts "woof woof"
  end
end

module Cat
  def speak
    puts "meow"
  end
end

module Module_manager
  attr_accessor :name
  def extend mod
    @ancestors ||= {}
    return if @ancestors[mod]
    remove @name if @name
    @name = mod
    mod_clone = mod.clone
    @ancestors[mod] = mod_clone
    super mod_clone
  end

  def remove mod
    mod_clone = @ancestors[mod]
    mod_clone.instance_methods.each {|m| mod_clone.module_eval {remove_method m } }
    @ancestors[mod] = nil
  end
end

class Animal
  include Module_manager
end

animal = Animal.new

animal.extend(Cat)
animal.speak # meow

animal.extend(Dog)
animal.speak # woof woof

animal.extend(Cat)
animal.speak # meow

animal.extend(Dog)
animal.speak # woof woof

animal.extend(Cat)
animal.speak # meow

Answer 2

, , .

class Animal
  include Dog
  alias :dog_speak :speak
  include Cat
  alias :cat_speak :speak
  private :dog_speak, :cat_speak

  def initialize
    @speak_to_me = [:cat_speak, :dog_speak].cycle
  end  

  def speak
    send @speak_to_me.next
  end
end

animal = Animal.new
  #=> #<Animal:0x007fe3a222b0e0 @speak_to_me=#<Enumerator:
  #     [:cat_speak, :dog_speak]:cycle>> 

animal.speak #-> meow
animal.speak #-> woof woof
animal.speak #-> meow
animal.speak #-> woof woof