標(biāo)簽： python 設(shè)計(jì)模式

引子

狀態(tài)模式確實(shí)很好玩，我是說(shuō)書上的例子確實(shí)很好玩，我對(duì)著電腦玩了好長(zhǎng)時(shí)間，但是想說(shuō)清楚還真不太容易，先從容易的開始吧

糖果機(jī)

糖果機(jī)操作的流程如下所示，這張圖也叫狀態(tài)圖，它顯示了糖果機(jī)的工作流程及狀態(tài)流程
狀態(tài)圖1

狀態(tài)圖.png-37kB

• 售出糖果
• 糖果售罄
• 有25分錢
• 沒有25分錢
  操作糖果機(jī)會(huì)設(shè)計(jì)四個(gè)動(dòng)作
• 投入25分錢
• 退回25分錢
• 轉(zhuǎn)動(dòng)曲柄
• 發(fā)放糖果 這個(gè)動(dòng)作是糖果機(jī)內(nèi)部的動(dòng)作，機(jī)器自己調(diào)用

一開始...

創(chuàng)建一個(gè)糖果機(jī)的類，包含了四種狀態(tài)

class GumballMachine:
    def __init__(self, count):
        self.SOLD_OUT = 0   #糖果售罄狀態(tài)
        self.NO_QUARTER = 1 #沒有25分錢狀態(tài)
        self.HAS_QUARTER = 2    #有25分錢狀態(tài)
        self.SOLD = 3   #售出糖果狀態(tài)
        self.state = self.SOLD_OUT  #初始狀態(tài)為`沒有25分錢狀態(tài)`
        self.count = count  #設(shè)置一個(gè)糖果數(shù)量變量，它為0時(shí)就是糖果售罄的狀態(tài)
        if self.count > 0:  #此處如果糖果數(shù)大于0，則狀態(tài)為初始狀態(tài)
            self.state = self.NO_QUARTER

接下來(lái)該怎么辦呢？
按照上圖，狀態(tài)與狀態(tài)之間是通過(guò)動(dòng)作進(jìn)行連接的，可以對(duì)每一個(gè)動(dòng)作創(chuàng)建一個(gè)對(duì)應(yīng)的方法，這些方法利用條件語(yǔ)句來(lái)決定在四個(gè)狀態(tài)下的恰當(dāng)行為
例如投入25分錢和這個(gè)動(dòng)作在四種狀態(tài)下糖果機(jī)的反應(yīng)如下圖
狀態(tài)圖2

狀態(tài)圖2.png-42.4kB

def insertQuarter(self):    #投入25分錢動(dòng)作
        if self.state == self.HAS_QUARTER:
            print("You cannot insert another quarter")
        elif self.state == self.NO_QUARTER:
            self.state = self.HAS_QUARTER
            print("You insert a quarter")
        elif self.state == self.SOLD_OUT:
            print("You can't insert a quarter, the machine is sold out")
        elif self.state == self.SOLD:
            print("Please wait, we're already giving you a gumball")

    def ejectQuarter(self):     #退回25分錢動(dòng)作
        if self.state == self.HAS_QUARTER:
            print("Quarter returned")
            self.state = self.NO_QUARTER
        elif self.state == self.NO_QUARTER:
            print("You haven't inserted a quarter")
        elif self.state == self.SOLD:
            print("Sorry, you already turned the crank")
        elif self.state == self.SOLD_OUT:
            print("You can't eject, you haven't inserted a quarter yet")

    def turnCrank(self):    #轉(zhuǎn)動(dòng)曲柄動(dòng)作
        if self.state == self.SOLD:
            print("Turning twice doesn't get you another gumball!")
        elif self.state == self.NO_QUARTER:
            print("You turned, but there's no quarter")
        elif self.state == self.SOLD_OUT:
            print("You turned, but there's no gumball")
        elif self.state == self.HAS_QUARTER:
            print("You turned....")
            self.state = self.SOLD
            self.dispense()     #切換到發(fā)放糖果這個(gè)內(nèi)部動(dòng)作上

    def dispense(self):     #發(fā)放糖果動(dòng)作
        if self.state == self.SOLD:
            print("A gumball comes rolling out the slot")
            self.count = self.count - 1     #發(fā)放一次糖果，糖果數(shù)量要減1
            if self.count == 0:    #糖果數(shù)量為0了，切換到糖果售罄的狀態(tài)
                print("Oops, out of gumballs")
                self.state = self.SOLD_OUT
            else:
                self.state = self.NO_QUARTER
        elif self.state == self.NO_QUARTER:
            print("You need to pay first")
        elif self.state == self.SOLD_OUT:
            print("No gumball dispense")
        elif self.state == self.HAS_QUARTER:
            print("No gumball dispense")

玩一玩....
可以增加兩個(gè)方法，玩的時(shí)候?qū)崟r(shí)查看當(dāng)前狀態(tài)和糖果數(shù)量

def getCount(self):
        print(self.count)
def getState(self):
        print(self.state)

按照下面方法玩

def main():
    gumballMachine = GumballMachine(2)
    gumballMachine.getCount()
    gumballMachine.getState()
    print("=====================================================")
    gumballMachine.insertQuarter()
    gumballMachine.getState()
    gumballMachine.ejectQuarter()
    gumballMachine.ejectQuarter()
    gumballMachine.insertQuarter()
    gumballMachine.getState()
    gumballMachine.turnCrank()
    gumballMachine.getState()
    gumballMachine.getCount()
    gumballMachine.insertQuarter()
    gumballMachine.turnCrank()
    gumballMachine.getState()
    print("=====================================================")
    gumballMachine.turnCrank()

返回的結(jié)果

2   #兩個(gè)糖果
1   #沒有25分錢狀態(tài)
=====================================================
You insert a quarter
2   #有25分錢狀態(tài)
Quarter returned
You haven't inserted a quarter
You insert a quarter
2   #有25分錢狀態(tài)
You turned....
A gumball comes rolling out the slot
1   #沒有25分錢狀態(tài)
1   #一個(gè)糖果
You insert a quarter
You turned....
A gumball comes rolling out the slot
Oops, out of gumballs
0   #糖果售罄狀態(tài)
=====================================================
You turned, but there's no gumball

這個(gè)時(shí)候如果又來(lái)了一個(gè)狀態(tài)怎么辦...
按照狀態(tài)2圖，需要增加一個(gè)新的狀態(tài)，之后在每個(gè)動(dòng)作里面增加針對(duì)這個(gè)狀態(tài)的行為，好像違反了好多設(shè)計(jì)原則。

新的方法

狀態(tài)是變化的量，將變化封裝起來(lái)，將動(dòng)作和行為放到狀態(tài)里，這樣每個(gè)狀態(tài)只要實(shí)現(xiàn)它自己的那套行為。
為每個(gè)狀態(tài)創(chuàng)建狀態(tài)類，這些類負(fù)責(zé)在對(duì)應(yīng)的動(dòng)作下糖果機(jī)的行為

將動(dòng)作和行為委托給狀態(tài)類

狀態(tài)圖3

狀態(tài)圖3.png-50.9kB

#有25分錢狀態(tài)
class HasQuarterState(object):
    def __init__(self, gumballMachine): #傳入糖果機(jī)的實(shí)例
        self.gumballMachine = gumballMachine
    def insertQuarter(self):    #投入25分錢動(dòng)作
        print("You cannot insert another quarter")
    def ejectQuarter(self):     #退出25分錢動(dòng)作
        print("Quarter returned")
        self.gumballMachine.setState(self.gumballMachine.getNoQuarterState())   #之后糖果機(jī)的狀
        #態(tài)切換到?jīng)]有25分錢狀態(tài)
    def turnCrank(self):    #轉(zhuǎn)動(dòng)曲柄動(dòng)作
        print("You turned....")
        self.gumballMachine.setState(self.gumballMachine.getSoldState())    #之后糖果機(jī)的狀
        #態(tài)切換到售出糖果狀態(tài)
    def dispense(self):     #發(fā)放糖果動(dòng)作，這是個(gè)內(nèi)部動(dòng)作，此處實(shí)現(xiàn)沒有作用
        print("No gumball dispense")

其他狀態(tài)的代碼也是類似

#糖果售罄狀態(tài)
class SoldOutState(object):
    def __init__(self, gumballMachine):
        self.gumballMachine = gumballMachine
    def insertQuarter(self):
        print("You can't insert a quarter, the machine is sold out")
    def ejectQuarter(self):
        print("You can't eject, you haven't inserted a quarter yet")
    def turnCrank(self):
        print("You turned, but there's no gumball")
    def dispense(self):
        print("No gumball dispense")
#沒有25分錢狀態(tài)
class NoQuarterState(object):
    def __init__(self, gumballMachine):
        self.gumballMachine = gumballMachine
    def insertQuarter(self):
        print("You inserted a quarter")
        self.gumballMachine.setState(self.gumballMachine.getHasQuarterState())
    def ejectQuarter(self):
        print("You haven't inserted a quarter")
    def turnCrank(self):
        print("You turned, but there's no quarter")
    def dispense(self):
        print("You need to pay first")
#售出糖果狀態(tài)        
class SoldState(object):
    def __init__(self, gumballMachine):
        self.gumballMachine = gumballMachine
    def insertQuarter(self):
        print("Please wait, we're already giving you a gumball")
    def ejectQuarter(self):
        print("Sorry, you already turned the crank")
    def turnCrank(self):
        print("Turning twice doesn't get you another gumball!")
    def dispense(self):
        self.gumballMachine.releaseBall()
        if self.gumballMachine.getCount()>0:
            self.gumballMachine.setState(self.gumballMachine.getNoQuarterState())
        else:
            print("Oops, out of gumballs")
            self.gumballMachine.setState(self.gumballMachine.getSoldOutState())

看看糖果機(jī)的實(shí)現(xiàn)

#糖果機(jī)類
class GumballMachine:
    def __init__(self, numberGumballs):
        self.count = numberGumballs
#=========創(chuàng)建每一個(gè)狀態(tài)的狀態(tài)實(shí)例====================#
        self.soldOutState = SoldOutState(self)
        self.noQuarterState = NoQuarterState(self)
        self.hasQuarterState = HasQuarterState(self)
        self.soldState = SoldState(self)
#=========end=========================================#
        if self.count > 0:
            self.state = self.noQuarterState
#============每個(gè)狀態(tài)的get方法和set方法===============#
    def getSoldOutState(self):
        return self.soldOutState
    def getNoQuarterState(self):
        return self.noQuarterState
    def getHasQuarterState(self):
        return self.hasQuarterState
    def getSoldState(self):
        return self.soldState
    def setState(self, state):
        self.state = state
#=========end=========================================#
#============將方法委托給當(dāng)前的狀態(tài)===================#
    def insertQuarter(self):
        self.state.insertQuarter()
    def ejectQuarter(self):
        self.state.ejectQuarter()
    def turnCrank(self):
        if self.state == self.hasQuarterState:
            self.state.turnCrank()
            self.state.dispense()
        else:
            self.state.turnCrank()
#=========end=========================================#
    def releaseBall(self):
        print("A gumball comes rolling out the slot...")
        if self.count != 0:
            self.count -= 1
#============檢查狀態(tài)和糖果數(shù)量的方法=================#
    def getState(self):
        print(self.state)
    def getCount(self):
        return self.count

還是用之前得測(cè)試代碼，看看返回

2   #糖果數(shù)量
<__main__.NoQuarterState object at 0x01D6BC90>      #當(dāng)前狀態(tài)
=====================================================
You inserted a quarter      #行為
<__main__.HasQuarterState object at 0x01D6BCB0>     #當(dāng)前狀態(tài)
Quarter returned        #行為
You haven't inserted a quarter      #行為
You inserted a quarter      #行為
<__main__.HasQuarterState object at 0x01D6BCB0>     #當(dāng)前狀態(tài)
You turned....      #行為
A gumball comes rolling out the slot...     #行為
<__main__.NoQuarterState object at 0x01D6BC90>      #當(dāng)前狀態(tài)
1       #糖果數(shù)量
You inserted a quarter      #行為
You turned....      #行為
A gumball comes rolling out the slot...     #行為
Oops, out of gumballs       #行為
<__main__.SoldOutState object at 0x01D6BC70>        #當(dāng)前狀態(tài)
=====================================================
You turned, but there's no gumball      #行為

看看執(zhí)行圖

執(zhí)行圖.png-59.2kB

再來(lái)一個(gè)狀態(tài)

增加一個(gè)游戲狀態(tài)，轉(zhuǎn)曲柄獲取糖果的時(shí)候，有10%的機(jī)會(huì)能成為大贏家，獲得附贈(zèng)的一粒糖果，這個(gè)怎么搞？
增加一個(gè)狀態(tài)winnerState

class WinnerState(object):
    def __init__(self, gumballMachine):
        self.gumballMachine = gumballMachine
    def insertQuarter(self):
        print("Please wait, we're already giving you a gumball")
    def ejectQuarter(self):
        print("Sorry, you already turned the crank")
    def turnCrank(self):
        print("Turning twice doesn't get you another gumball!")
    # 你贏了，如果糖果沒了，那就算了，只能白贏了；
    def dispense(self):
        print("You are winner! You get 2 gumball for youe quarter")
        if self.gumballMachine.getCount()==0:
            self.gumballMachine.setState(self.gumballMachine.getSoldOutState())
        else:
            self.gumballMachine.releaseBall()
            if self.gumballMachine.getCount()>0:
                self.gumballMachine.releaseBall()
                self.gumballMachine.setState(self.gumballMachine.getNoQuarterState())
            else:
                print("Oops, out of gumballs")
                self.gumballMachine.setState(self.gumballMachine.getSoldOutState())

隨機(jī)數(shù)怎么整，random.randint這個(gè)就能實(shí)現(xiàn)，但是這個(gè)動(dòng)作要增加在哪里呢，哪個(gè)狀態(tài)下轉(zhuǎn)動(dòng)曲柄可以獲得糖果，是有25分錢這個(gè)狀態(tài)，只要將這個(gè)狀態(tài)下的轉(zhuǎn)曲柄動(dòng)作稍微改動(dòng)一下就OK了

def turnCrank(self):
        print("You turned....")
        #產(chǎn)生隨機(jī)數(shù)
        self.winner = random.randint(1, 100)
        #這個(gè)數(shù)為1你就贏了
        if self.winner == 1:
            self.gumballMachine.setState(self.gumballMachine.getWinnerState())
        else:
            self.gumballMachine.setState(self.gumballMachine.getSoldState())

開始玩吧

def main():
    gumballMachine = GumballMachine(100)
    print(gumballMachine.getCount())
    for i in range(5):
        print("======================{0}====================".format(i+1))
        gumballMachine.insertQuarter()
        gumballMachine.turnCrank()
    print(gumballMachine.getCount())

5次幾率好像太小，應(yīng)該中不了

======================1====================
You inserted a quarter
You turned....
You are winner! You get 2 gumball for youe quarter
A gumball comes rolling out the slot...
A gumball comes rolling out the slot...
======================2====================
You inserted a quarter
You turned....
A gumball comes rolling out the slot...
======================3====================
You inserted a quarter
You turned....
A gumball comes rolling out the slot...
======================4====================
You inserted a quarter
You turned....
A gumball comes rolling out the slot...
======================5====================
You inserted a quarter
You turned....
A gumball comes rolling out the slot...
94

靠?。。。?！第一次就中了

定義

狀態(tài)模式允許對(duì)象在內(nèi)部狀態(tài)改變時(shí)改變它的行為，對(duì)象看起來(lái)好像修改了它的類