strategy.rb

require "interface"

Strategy = interface {
  required_methods :use
}

class StrategyOne
  implements Strategy
  
  def use
    puts "This is first case"
  end
end

class StrategyTwo
  implements Strategy
  
  def use
    puts "This is second case"
  end
end

class Contex
  attr_accessor :strategy
  def initialize(strategy)
    @strategy = strategy
  end
  
  def get_case
    @strategy.use
  end
end

contex = Contex.new(StrategyOne.new)
contex.get_case