A basic strategy pattern example in Ruby.

strategy.rb

class Duck
  def initialize(name = "Ducky")
    set_quack
    @name = name
  end
  
  def quack
    @quack_behavior.quack
  end
  
  def set_quack(behavior = LoudQuack.new)
    if behavior.respond_to?(:set_duck)
      behavior.set_duck(self)
    end
    @quack_behavior = behavior
  end
  
  def name
    return @name
  end
end

class LoudQuack
  def quack
    puts "QUACK!!!!"
  end
end

class QuietQuack
  def quack
    puts "quack...."
  end
end

class NameQuack
  def set_duck(duck)
    @myduck = duck
  end
  
  def quack
    puts @myduck.name
  end
end

norm = Duck.new
norm.quack

norm.set_quack(QuietQuack.new)
norm.quack

norm.set_quack(NameQuack.new)
norm.quack