设计模式十七（状态模式，python语言实现）

基本理论请参考相应书籍，这里直接给实例

 基本说明：电梯（Context）内部维护着电梯的运行状态，如在几楼等信息。

                  state是电梯状态的的父类。子类有FloorA（一楼状态），FloorB（二楼状态）FloorC（三楼状态），FloorD（四楼状态）

 客户端选择要去的楼层，电梯根据当前的状态决定是需要上行还是需要下行，并判断是否到目的地。

 

# -*- coding: utf-8 -*-######################################################## # state.py# Python implementation of the Class Context# Generated by Enterprise Architect# Created on:      13-十二月-2012 14:23:46# #######################################################from __future__ import divisionfrom __future__ import print_functionfrom __future__ import unicode_literalsfrom future_builtins import *class State(object):    """This class defines an interface for encapsulating the behaviour associated with    a particular state of the Context.    """    m_obj=None    def __init__(self, state=0):        self.state=state        self.current=None        self.up=None        self.down=None        pass    def Handle(self,state):        if self.state==state:            print('第%d' %self.state+'楼到了，请下电梯' )            State.m_obj=self             pass        else:            self.SetContext()            if self.state<state:                print('正经过第%d' %self.state+'楼，电梯继续上行')                self.current=self.up                pass            else:                print('正经过第%d' %self.state+'楼，电梯继续下行')                self.current=self.down                pass            self.current.Handle(state)            pass        return State.m_obj        pass        def SetFloor(self, floor):                pass    def SetContext(self):        passclass FloorA(State):    """This class defines an interface for encapsulating the behaviour associated with    a particular state of the Context.    """    def __init__(self, state=1):        super(FloorA,self).__init__(state)        pass    def SetContext(self):        self.up=FloorB()        self.down=None               pass    def SetFloor(self, floor):        passclass FloorB(State):    """This class defines an interface for encapsulating the behaviour associated with    a particular state of the Context.    """    def __init__(self, state=2):        super(FloorB,self).__init__(state)        pass    def SetContext(self):        self.up=FloorC()        self.down=FloorA()        pass    def SetFloor(self, floor):        passclass FloorC(State):    """This class defines an interface for encapsulating the behaviour associated with    a particular state of the Context.    """    def __init__(self, state=3):        super(FloorC,self).__init__(state)        pass    def SetContext(self):        self.up=FloorD()        self.down=FloorB()                pass    def SetFloor(self, floor):        passclass FloorD(State):    """This class defines an interface for encapsulating the behaviour associated with    a particular state of the Context.    """    def __init__(self, state=4):        super(FloorD,self).__init__(state)        pass    def SetContext(self):        self.up=None        self.down=FloorC()                pass    def SetFloor(self, floor):        pass            class Context(object):    """This class defines the interface of interest to clients and maintains an    instance of a ConcreteState subclass that defines the current state.    """    m_State= State()        def __init__(self):        Context.m_State=FloorA()        pass    def SetState(self,state):        Context.m_State=state        pass    def Request(self,floor):        # state->Handle()        print('电梯在第%d楼'%Context.m_State.state)                current=Context.m_State.Handle(floor)        if current!=None:            self.SetState(current)            pass        else:            print('电梯运行出错')            pass                        print('\n')                        pass    passif(__name__=="__main__"):      #建立电梯    m_Context= Context()    #到四楼     m_Context.Request(4)    #然后有人到2楼         m_Context.Request(2)    #然后有人到3楼    m_Context.Request(3)    #然后有人到1楼    m_Context.Request(1) 

运行结果：