How do you do polymorphism in Ruby?

Question

In C#, I can do this:

class Program
{
    static void Main(string[] args)
    {
        List animals = new List();

        anima         


        

Answer 1

There's a method becomes which implements a polymorphism (by coping all instance variables from given class to new one)

class Animal
  attr_reader :name

  def initialize(name = nil)
    @name = name
  end

  def make_noise
    ''
  end

  def becomes(klass)
    became = klass.new
    became.instance_variables.each do |instance_variable|
      value = self.instance_variable_get(instance_variable)
      became.instance_variable_set(instance_variable, value)
    end

    became
  end
end

class Dog < Animal
  def make_noise
    'Woof'
  end
end

class Cat < Animal
  def make_noise
    'Meow'
  end
end

animals = [Dog.new('Spot'), Cat.new('Tom')]

animals.each do |animal|
  new_animal = animal.becomes(Cat)
  puts "#{animal.class} with name #{animal.name} becomes #{new_animal.class}"
  puts "and makes a noise: #{new_animal.make_noise}"
  puts '----'
end

and result is:

Dog with name Spot becomes Cat
and makes a noise: Meow
----
Cat with name Tom becomes Cat
and makes a noise: Meow
----

• A polymorphism could be useful to avoid if statement (antiifcampaign.com)

• If you use RubyOnRails becomes method is already implemented: becomes

• Quicktip: if you mix polymorphism with STI it brings you the most efficient combo to refactor your code

I wish it helped you

Answer 2

A little variant of manveru's solution which dynamic create different kind of object based in an array of Class types. Not really different, just a little more clear.

Species = [Dog, Cat]

Species.each do |specie|
  animal = specie.new   # this will create a different specie on each call of new
  print animal.MakeNoise + "\n"
  animal.Sleep
end