ruby: Factory Method Pattern

README.md

Factory Method Pattern

Duck Duck0 says Quack!
Duck Duck1 says Quack!
Duck Duck2 says Quack!
Duck Duck0 is eating.
Duck Duck1 is eating.
Duck Duck2 is eating.
Duck Duck0 sleeps quietly.
Duck Duck1 sleeps quietly.
Duck Duck2 sleeps quietly.

==========================================================================================
Template Method

Duck Animal0 says Quack!
Duck Animal1 says Quack!
Duck Animal2 says Quack!
Duck Animal0 is eating.
Duck Animal1 is eating.
Duck Animal2 is eating.
Duck Animal0 sleeps quietly.
Duck Animal1 sleeps quietly.
Duck Animal2 sleeps quietly.
Frog Animal0 says Crooooaaaak!
Frog Animal1 says Crooooaaaak!
Frog Animal2 says Crooooaaaak!
Frog Animal0 is eating.
Frog Animal1 is eating.
Frog Animal2 is eating.
Frog Animal0 doesn't sleep; he croaks all night!
Frog Animal1 doesn't sleep; he croaks all night!
Frog Animal2 doesn't sleep; he croaks all night!

==========================================================================================
Parameterized Factory Method

The water lily Plant0 floats, soaks up the sun, and grows
The water lily Plant1 floats, soaks up the sun, and grows
Duck Animal0 says Quack!
Duck Animal1 says Quack!
Duck Animal2 says Quack!
Duck Animal0 is eating.
Duck Animal1 is eating.
Duck Animal2 is eating.
Duck Animal0 sleeps quietly.
Duck Animal1 sleeps quietly.
Duck Animal2 sleeps quietly.
The Algae Plant0 soaks up the sun and grows
The Algae Plant1 soaks up the sun and grows
Frog Animal0 says Crooooaaaak!
Frog Animal1 says Crooooaaaak!
Frog Animal2 says Crooooaaaak!
Frog Animal0 is eating.
Frog Animal1 is eating.
Frog Animal2 is eating.
Frog Animal0 doesn't sleep; he croaks all night!
Frog Animal1 doesn't sleep; he croaks all night!
Frog Animal2 doesn't sleep; he croaks all night!

==========================================================================================
Parameterized Factory Method, next steps

The water lily Plant0 floats, soaks up the sun, and grows
The water lily Plant1 floats, soaks up the sun, and grows
Duck Animal0 says Quack!
Duck Animal1 says Quack!
Duck Animal2 says Quack!
Duck Animal0 is eating.
Duck Animal1 is eating.
Duck Animal2 is eating.
Duck Animal0 sleeps quietly.
Duck Animal1 sleeps quietly.
Duck Animal2 sleeps quietly.
The Algae Plant0 soaks up the sun and grows
The Algae Plant1 soaks up the sun and grows
Frog Animal0 says Crooooaaaak!
Frog Animal1 says Crooooaaaak!
Frog Animal2 says Crooooaaaak!
Frog Animal0 is eating.
Frog Animal1 is eating.
Frog Animal2 is eating.
Frog Animal0 doesn't sleep; he croaks all night!
Frog Animal1 doesn't sleep; he croaks all night!
Frog Animal2 doesn't sleep; he croaks all night!

==========================================================================================
Factory Method

The water lily Plant0 floats, soaks up the sun, and grows
The water lily Plant1 floats, soaks up the sun, and grows
Duck Animal0 says Quack!
Duck Animal1 says Quack!
Duck Animal2 says Quack!
Duck Animal0 is eating.
Duck Animal1 is eating.
Duck Animal2 is eating.
Duck Animal0 sleeps quietly.
Duck Animal1 sleeps quietly.
Duck Animal2 sleeps quietly.
The Algae Plant0 soaks up the sun and grows
The Algae Plant1 soaks up the sun and grows
Frog Animal0 says Crooooaaaak!
Frog Animal1 says Crooooaaaak!
Frog Animal2 says Crooooaaaak!
Frog Animal0 is eating.
Frog Animal1 is eating.
Frog Animal2 is eating.
Frog Animal0 doesn't sleep; he croaks all night!
Frog Animal1 doesn't sleep; he croaks all night!
Frog Animal2 doesn't sleep; he croaks all night!

factory_method.rb

module FactoryMethod
  module V1
    class Duck
      def initialize(name)
        @name = name
      end

      def eat
        puts("Duck #{name} is eating.")
      end

      def speak
        puts("Duck #{name} says Quack!")
      end

      def sleep
        puts("Duck #{name} sleeps quietly.")
      end

      private

      attr_reader :name
    end

    class Frog
      def initialize(name)
        @name = name
      end

      def eat
        puts("Frog #{name} is eating.")
      end

      def speak
        puts("Frog #{name} says Crooooaaaak!")
      end

      def sleep
        puts("Frog #{name} doesn't sleep; he croaks all night!")
      end

      private

      attr_reader :name
    end

    class Pond
      def initialize(number_ducks)
        @ducks = []
        number_ducks.times do |i|
          duck = Duck.new("Duck#{i}")
          ducks << duck
        end
      end

      def simulate_on_day
        ducks.each { |duck| duck.speak }
        ducks.each { |duck| duck.eat }
        ducks.each { |duck| duck.sleep }
      end

      private

      attr_reader :ducks
    end
  end

  module V2
    class Pond
      def initialize(number_animals)
        @animals = []
        number_animals.times do |i|
          animal = new_animal("Animal#{i}")
          animals << animal
        end
      end

      def simulate_on_day
        animals.each { |animal| animal.speak }
        animals.each { |animal| animal.eat }
        animals.each { |animal| animal.sleep }
      end

      private

      attr_reader :animals
    end

    class DuckPond < Pond
      def new_animal(name)
        V1::Duck.new(name)
      end
    end

    class FrogPond < Pond
      def new_animal(name)
        V1::Frog.new(name)
      end
    end
  end

  module V3
    class Algae
      def initialize(name)
        @name = name
      end

      def grow
        puts("The Algae #{name} soaks up the sun and grows")
      end

      private

      attr_reader :name
    end

    class WaterLily
      def initialize(name)
        @name = name
      end

      def grow
        puts("The water lily #{name} floats, soaks up the sun, and grows")
      end

      private

      attr_reader :name
    end

    class Pond
      def initialize(number_animals, number_plants)
        @animals = []
        number_animals.times do |i|
          animal = new_animal("Animal#{i}")
          animals << animal
        end

        @plants = []
        number_plants.times do |i|
          plant = new_plant("Plant#{i}")
          plants << plant
        end
      end

      def simulate_on_day
        plants.each { |plant| plant.grow }
        animals.each { |animal| animal.speak }
        animals.each { |animal| animal.eat }
        animals.each { |animal| animal.sleep }
      end

      private

      attr_reader :animals, :plants
    end

    class DuckWaterLilyPond < Pond
      def new_animal(name)
        V1::Duck.new(name)
      end

      def new_plant(name)
        WaterLily.new(name)
      end
    end

    class FrogAlgaePond < Pond
      def new_animal(name)
        V1::Frog.new(name)
      end

      def new_plant(name)
        Algae.new(name)
      end
    end
  end

  module V4
    class Pond < V3::Pond
      def initialize(number_animals, number_plants)
        @animals = []
        number_animals.times do |i|
          animal = new_organism(:animal, "Animal#{i}")
          animals << animal
        end

        @plants = []
        number_plants.times do |i|
          plant = new_organism(:plant, "Plant#{i}")
          plants << plant
        end
      end

      private

      attr_reader :animals, :plants
    end

    class DuckWaterLilyPond < Pond
      def new_organism(type, name)
        if type == :animal
          V1::Duck.new(name)
        elsif type == :plant
          V3::WaterLily.new(name)
        else
          raise "Unknown organism type: #{type}"
        end
      end
    end

    class FrogAlgaePond < Pond
      def new_organism(type, name)
        if type == :animal
          V1::Frog.new(name)
        elsif type == :plant
          V3::Algae.new(name)
        else
          raise "Unknown organism type: #{type}"
        end
      end
    end
  end

  module V5
    class Pond < V4::Pond
      def initialize(number_animals, animal_class, number_plants, plant_class)
        @animal_class = animal_class
        @plant_class = plant_class

        @animals = []
        number_animals.times do |i|
          animal = new_organism(:animal, "Animal#{i}")
          animals << animal
        end

        @plants = []
        number_plants.times do |i|
          plant = new_organism(:plant, "Plant#{i}")
          plants << plant
        end
      end

      def new_organism(type, name)
        if type == :animal
          animal_class.new(name)
        elsif type == :plant
          plant_class.new(name)
        else
          raise "Unknown organism type: #{type}"
        end
      end

      private

      attr_reader :animal_class, :plant_class
      attr_reader :animals, :plants
    end
  end
end

number_ducks = 3
number_animals = 3

#FactoryMethod::V1::Duck.new('Donald').eat
#FactoryMethod::V1::Frog.new('Pepe').eat

pond = FactoryMethod::V1::Pond.new(number_ducks)
pond.simulate_on_day

puts <<-EOF

==========================================================================================
Template Method

EOF

pond = FactoryMethod::V2::DuckPond.new(number_animals)
pond.simulate_on_day

pond = FactoryMethod::V2::FrogPond.new(number_animals)
pond.simulate_on_day

puts <<-EOF

==========================================================================================
Parameterized Factory Method

EOF

number_plants = 2

pond = FactoryMethod::V3::DuckWaterLilyPond.new(number_animals, number_plants)
pond.simulate_on_day

pond = FactoryMethod::V3::FrogAlgaePond.new(number_animals, number_plants)
pond.simulate_on_day

puts <<-EOF

==========================================================================================
Parameterized Factory Method, next steps

EOF

pond = FactoryMethod::V4::DuckWaterLilyPond.new(number_animals, number_plants)
pond.simulate_on_day

pond = FactoryMethod::V4::FrogAlgaePond.new(number_animals, number_plants)
pond.simulate_on_day

puts <<-EOF

==========================================================================================
Factory Method

EOF

pond = FactoryMethod::V5::Pond.new(number_animals, FactoryMethod::V1::Duck,
                                   number_plants, FactoryMethod::V3::WaterLily)
pond.simulate_on_day

pond = FactoryMethod::V5::Pond.new(number_animals, FactoryMethod::V1::Frog,
                                   number_plants, FactoryMethod::V3::Algae)
pond.simulate_on_day