裝飾器（Decorator）

目的：

將額外權責動態附加於物件身上，不必衍生子類別即可彈性增廣功能

結構：

程式碼範例：

class Component
  def operation
    raise NotImplementedError, "#{self.class} has not implemented method '#{__method__}'"
  end
end

class ConcreteComponent < Component
  def operation
    'ConcreteComponent'
  end
end

class Decorator < Component
  attr_accessor :component

  def initialize(component)
    @component = component
  end

  def operation
    @component.operation
  end
end

class ConcreteDecoratorA < Decorator
  def operation
    "ConcreteDecoratorA(#{@component.operation})"
  end
end

class ConcreteDecoratorB < Decorator
  def operation
    "ConcreteDecoratorB(#{@component.operation})"
  end
end

def client_code(component)
  print "RESULT: #{component.operation}"
end

simple = ConcreteComponent.new
puts 'Client: I\'ve got a simple component:'
client_code(simple)
puts "\n\n"


decorator1 = ConcreteDecoratorA.new(simple)
decorator2 = ConcreteDecoratorB.new(decorator1)
puts 'Client: Now I\'ve got a decorated component:'
client_code(decorator2)

解釋

這裡之所以不用繼承的原因在於，過多的組合會產出太多子類別繼承，而且繼承是屬於靜態（無法在過程中改變物件行為）所以使用組合方式進行

文章不定期更新！（umm ... 最近比較忙碌所以沒辦法紀錄太多，但會在之後陸續補充與將內容完整

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