Python适配器模式代码实现解析

Python适配器模式，代码，思考等

# -*- coding: utf-8 -*-
# author：baoshan
class Computer:
  def __init__(self, name):
    self.name = name
  def __str__(self):
    return 'the {} computer'.format(self.name)
  def execute(self):
    return 'executes a program'
class Synthesizer:
  def __init__(self, name):
    self.name = name
  def __str__(self):
    return 'the {} synthesizer'.format(self.name)
  def play(self):
    return 'is playing an electronic song'
class Human:
  def __init__(self, name):
    self.name = name
  def __str__(self):
    return '{} the human'.format(self.name)
  def speak(self):
    return 'says hello'
class Adapter:
  def __init__(self, obj, adapted_methods):
    self.obj = obj
    self.__dict__.update(adapted_methods)
def __str__(self):
    return str(self.obj)
def main():
  objects = [Computer('Asus')]
  synth = Synthesizer('moog')
  objects.append(Adapter(synth, dict(execute=synth.play)))
  human = Human('Bob')
  objects.append(Adapter(human, dict(execute=human.speak)))
  for i in objects:
    print('{} {}'.format(str(i), i.execute()))
if __name__ == '__main__':
  main()

代码输出：

the Asus computer executes a program
the moog synthesizer is playing an electronic song
Bob the human says hello

------------------------------------------------------------------------------------------

我们设法使得Human和Synthesizer类与客户端所期望的接口兼容，且无需改变它们的源代码。这太棒了!

这里有一个为你准备的挑战性练习，当前的实现有一个问题，当所有类都有一个属性name时，以下代码会运行失败。

for i in objects:
    print('{}'.format(i.name))

首先想想这段代码为什么会失败?虽然从编码的角度来看这是有意义的，但对于客户端代码来说毫无意义，客户端不应该关心“适配了什么”和“什么没有被适配”这类细节。我们只是想提供一个统一的接口。该如何做才能让这段代码生效?

思考一下如何将未适配部分委托给包含在适配器类中的对象。

答案如下：

将适配器类更改如下，增加一行代码

class Adapter:
  def __init__(self, obj, adapted_methods):
    self.obj = obj
    self.__dict__.update(adapted_methods)
    self.name = obj.name
  def __str__(self):
    return str(self.obj)

然后在main函数中获取对应的name，如下

def main():
  objects = [Computer('Asus')]
  synth = Synthesizer('moog')
  objects.append(Adapter(synth, dict(execute=synth.play)))
  human = Human('Bob')
  objects.append(Adapter(human, dict(execute=human.speak)))
  for i in objects:
    print('{} {}'.format(str(i), i.execute()))
    print('{}'.format(i.name))
if __name__ == '__main__':
  main()

输出结果如下：

the Asus computer executes a program
Asus
the moog synthesizer is playing an electronic song
moog
Bob the human says hello
Bob

参考自：《精通Python设计模式》

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