Python设计模式——状体模式

需求，根据当前的时间，返回工作状态

#encoding=utf-8
__author__ = 'kevinlu1010@qq.com'

def get_state(hour):
    if hour>=8 and hour<=12:
        return '上午工作，精神百倍'
    elif hour>12 and hour<=14:
        return '中午工作，困，想午休'
    elif hour>14 and hour<=18:
        return '下午工作，状态不错'
    elif hour>18 and hour<=20:
        return '加班了，状态不太好'
    else:
        return '不行了，要睡觉了'
if __name__=='__main__':

    for hour in (9,11,12,13,14,17,19,22,23):
        print '%d点，'%hour,get_state(hour)

缺点是，如果状态非常多时，（现在是5种），这段代码将会非常长，所以后期维护就比较困难

状态模式

#encoding=utf-8
__author__ = 'kevinlu1010@qq.com'

from abc import ABCMeta, abstractmethod

class State():
    __metaclass__ = ABCMeta

    @abstractmethod
    def write_code(self):
        pass

class Morning(State):
    def write_code(self, work):
        if work.hour <= 12 and work.hour > 8:
            print '上午工作，精神百倍'
        else:

            work.set_status(Noon())
            work.write_code(work)

class Noon(State):
    def write_code(self, work):
        if work.hour <= 14 and work.hour>12 :
            print '中午工作，困，想午休'
        else:
            work.set_status(Afternoon())
            work.write_code(work)

class Afternoon(State):
    def write_code(self, work):
        if work.hour <= 18 and work.hour>14:
            print '下午工作，状态不错'
        else:
            work.set_status(Eve())
            work.write_code(work)

class Eve(State):
    def write_code(self, work):
        if work.hour <= 22 and work.hour>18:
            print '加班了，状态不太好'
        else:
            work.set_status(Night())
            work.write_code(work)

class Night(State):
    def write_code(self, work):
        if work.hour <= 8 or work.hour > 22:
            print '不行了，要睡觉了'
        else:
            work.set_status(Morning())
            work.write_code(work)

class Work():
    def __init__(self, hour):
        self.hour = hour
        self.state = Morning()

    def set_status(self, state):
        self.state = state

    def write_code(self, work):
        self.state.write_code(work)

if __name__ == '__main__':
    work = Work(10)
    for hour in (9, 11, 12, 13, 14, 17, 19, 22, 23,12):
        work.hour = hour
        print '%d点，' % hour
        work.write_code(work)

状态模式中，定义一个状态的抽象类，为每一种状态建一个类，类中有一个handle函数（这里是write_code），来根据work的时间来做相应的处理，这种做的好处是十分灵活，每个状态都有自己的判断逻辑。拓展和维护起来都比较方便。