Python：设计模式之状态模式

# -*- coding: utf-8 -*-
from abc import ABCMeta, abstractmethod
class State(metaclass=ABCMeta):
    @abstractmethod
    def do_this(self):
        pass
class StartState(State):
    def do_this(self):
        print("start state")
class StopState(State):
    def do_this(self):
        print("stop state")
class TVContext(State):
    def __init__(self):
        self.state = None
    def get_state(self):
        return self.state
    def set_state(self, state):
        self.state = state
    def do_this(self):
        self.state.do_this()
if __name__ == '__main__':
    context = TVContext()
    start = StartState()
    stop = StopState()
    context.set_state(start)
    context.do_this()
    context.set_state(stop)
    context.do_this()
"""
start state
stop state
"""

# -*- coding: utf-8 -*-
# 接口
class ComputerState(object):
    name = "state"
    allowed = []
    def switch(self, state):
        if state.name in self.allowed:
            print("switch state: {}".format(state.name))
            self.__class__ = state
        else:
            print("state not allowed")
    def __str__(self):
        return self.name
# 具体实现
# 开机
class On(ComputerState):
    name = "on"
    allowed = ["off", "hibernate"]
# 关机
class Off(ComputerState):
    name = "off"
    allowed = ["on"]
# 休眠
class Hibernate(ComputerState):
    name = "hibernate"
    allowed = ["on", "off"]
# 客户端
class Computer(object):
    def __init__(self):
        self.state = Off()  # 初始状态是关机状态
    def change(self, state):
        self.state.switch(state)
if __name__ == '__main__':
    computer = Computer()
    # 开机 -> 休眠 -> 关机
    computer.change(On)
    computer.change(Hibernate)
    computer.change(Off)
    # 关机的请情况下休眠
    computer.change(Hibernate)
"""
switch state: on
switch state: hibernate
switch state: off
state not allowed
"""