state_pattern.py

#!/usr/bin/env python
# -*- coding:utf-8 -*-

__author__ = 'Andy'
"""
大话设计模式
设计模式——状态模式
状态模式(State Pattern):当一个对象的内在状态改变时允许改变其行为，这个对象看起来像是改变了其类
应用场景:当控制一个对象的状态转换的条件表达式过于复杂时,把状态的判断逻辑转移到表示不同状态的一系列类当中,可以把复杂的判断逻辑简化
(当一个对象的行为取决于它的状态,并且它必须在运行时刻根据状态改变他的行为)
"""
class State(object):
	def __init__(self):
		pass

	def write_program(self, w):
		pass

class Work(object):

	def __init__(self):
		self.hour = 9
		self.curr = ForenoonState()

	def set_state(self, s):
		self.curr = s

	def write_program(self):
		self.curr.write_program(self)


class ForenoonState(State):

	def write_program(self, w):
		if w.hour < 12:
			print "当前时间:%s点,"%w.hour,"精神百倍"
		else:
			w.set_state(AfternoonState())
			w.write_program()

class AfternoonState(State):

	def write_program(self, w):
		if w.hour < 17:
			print "当前时间:%s点,"%w.hour,"状态还行,继续努力"
		else:
			w.set_state(EveningState())
			w.write_program()

class EveningState(State):

	def write_program(self, w):
		if w.hour < 21:
			print "当前时间:%s点,"%w.hour,"加班呢,疲劳了"
		else:
			w.set_state(SleepState())
			w.write_program()


class SleepState(State):

	def write_program(self, w):
		print "当前时间:%s点,"%w.hour,"不行了,睡着了"

if __name__=="__main__":
	work = Work()
	work.hour = 9
	work.write_program()
	work.hour = 15
	work.write_program()
	work.hour = 20
	work.write_program()
	work.hour = 22
	work.write_program()