strategy pattern dynamic behavior example

strategy_pattern.rb

module RunStrategies
  class RunStrategyInterface
    def self.run(name)
      raise "Run method has not been implemented!"
    end
  end

  class Jog < RunStrategyInterface
    def self.run(name)
      puts "#{name} is now jogging at a comfortable pace."
    end
  end

  class Sprint < RunStrategyInterface
    def self.run(name)
      puts "#{name} is now sprinting full speeed!"
    end
  end

  class Marathon < RunStrategyInterface
    def self.run(name)
      puts "#{name} is now running at a steady pace."
    end
  end
end

class Runner
  attr_reader :name, :strategy
  attr_writer :strategy
  
  def initialize(name, strategy)
    @name = name
    @strategy = strategy
  end

  def run
    @strategy.run(@name)
  end
end

class Race
  attr_reader :runners

  def initialize(runners)
    @runners = runners
  end

  def start
    @runners.each { |runner| runner.run }
  end
end

alice_ruby = Runner.new("Alice Ruby", RunStrategies::Jog)
florence_joyner = Runner.new("Florence Joyner", RunStrategies::Sprint)
eliud_kipchoge = Runner.new("Eliud Kipchoge", RunStrategies::Marathon)

race = Race.new([alice_ruby, florence_joyner, eliud_kipchoge])
race.start

This pattern is particularly useful when you have an object that needs to be able to execute a single behavior in different ways at different times.