bridge.py

#!/usr/bin/env python
# encoding: utf-8
"""
桥接模式

将抽象部分与它的实现部分分离, 使它们都可以独立地变化

- 独立变化
"""

from abc import ABCMeta, abstractmethod


class Implementor(object):
    __metaclass__ = ABCMeta

    @abstractmethod
    def operation(self):
        pass


class ConcreteImplementorA(Implementor):
    def operation(self):
        print "plan A"


class ConcreteImplementorB(Implementor):
    def operation(self):
        print "plan B"


class Abstraction(object):
    def __init__(self, implementor=None):
        if implementor is not None:
            self.__implementor = implementor

    @property
    def implementor(self):
        return self.__implementor

    @implementor.setter
    def implementor(self, value):
        self.__implementor = value

    def operation(self):
        self.__implementor.operation()


class RefinedAbstraction(Abstraction):
    pass


if __name__ == '__main__':
    ab = RefinedAbstraction()

    ab.implementor = ConcreteImplementorA()
    ab.operation()

    ab.implementor = ConcreteImplementorB()
    ab.operation()