Adapter pattern in crystal-lang

adaptor.cr

class Demo
  @obj: Coin
  def initialize(name : String)
    if name == "LTC"
      @obj = LTC.new
    elsif name == "ETH"
      @obj = ETH.new
    else
      raise "Not found name"
    end  
  end 

  def exec(name : String)
    @obj.exec(name)
  end 
end

abstract class Coin
  abstract def exec(name : String)
end

class LTC < Coin
  def initialize
  end
  
  def exec(name : String)
    puts "Im LTC: #{name}"
  end  
end

class ETH < Coin
  def initialize
  end
  
  def exec(name : String)
    puts "Im ETH: #{name}"
  end  
end

demo = Demo.new("ETH")
demo.exec("hello")

demo = Demo.new("LTC")
demo.exec("hello")