Python适配器模式，代码，思考等

# -*- coding: utf-8 -*-# author：baoshanclass 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 programthe moog synthesizer is playing an electronic songBob the human says hello

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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 programAsusthe moog synthesizer is playing an electronic songmoogBob the human says helloBob

参考自：《精通Python设计模式》

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