Python设计模式-中介者模式

代码基于3.5.2，代码如下;

#coding:utf-8#中介者模式class colleague():    mediator = None    def __init__(self,mediator):        self.mediator = mediatorclass purchaseColleague(colleague):    def buyStuff(self,num):        print("PURCHASE:Bought {0}".format(num))        self.mediator.execute("buy",num)    def getNotice(self,content):        print("PURCHASE:Get Notice -- {0}".format(content))class warehoustColleague(colleague):    total = 0    threshold = 100    def setThreshold(self,threshold):        self.threshold = threshold    def isEnough(self):        if self.total < self.threshold:            print("WARNING:Warning ... Stock is low ..")            self.mediator.execute("warning",self.total)            return False        else:            return True    def inc(self,num):        self.total += num        print("WAREHOUSE:Increase {0}".format(num))        self.mediator.execute("increase",num)    def dec(self,num):        if num > self.total:            print("WAREHOUSE：Error ... Stock is not enough")        else:            self.total -= num            print("WAREHOUSE:Decrease {0}".format(num))            self.mediator.execute("decrease",num)        self.isEnough()class salesColleague(colleague):    def sellStuff(self,num):        print("SALES:Sell {0}".format(num))        self.mediator.execute("sell",num)    def getNotice(self,content):        print("SALES:Get Notice -- {0}".format(content))class abstractMediator():    purchase = None    sales = None    warehouse = None    def setPurchase(self,purchase):        self.purchase = purchase    def setWarehouse(self,warehouse):        self.warehouse = warehouse    def setSales(self,sales):        self.sales = sales    def execute(self,content,num):        passclass stockMediator(abstractMediator):    def execute(self,content,num):        print("MEDIATOR:Get Info -- {0}".format(content))        if content == "buy":            self.warehouse.inc(num)            self.sales.getNotice("Bought {0}".format(num))        elif content == "increase":            self.sales.getNotice("Inc {0}".format(num))            self.purchase.getNotice("Inc {0}".format(num))        elif content == "decrease":            self.sales.getNotice("Dec {0}".format(num))            self.purchase.getNotice("Dec {0}".format(num))        elif content == "warning":            self.sales.getNotice("Stock is low {0} left".format(num))            self.purchase.getNotice("Stock is low. Please Buy More {0}".format(num))        elif content == "sell":            self.warehouse.dec(num)            self.purchase.getNotice("Sold {0}".format(num))        else:            passif __name__ == "__main__":    mobile_mediator = stockMediator()    mobile_purchase = purchaseColleague(mobile_mediator)    moblie_warehouse = warehoustColleague(mobile_mediator)    moblie_sales = salesColleague(mobile_mediator)    mobile_mediator.setPurchase(mobile_purchase)    mobile_mediator.setWarehouse(moblie_warehouse)    mobile_mediator.setSales(moblie_sales)    moblie_warehouse.setThreshold(200)    mobile_purchase.buyStuff(300)    moblie_sales.sellStuff(120)

中介者模式分析与解读

中介者模式

中介者模式，用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。

代码解读

该例子基于的需求:销售一旦达成订单，销售人员会通过系统的销售子系统部分通知仓储子系统，仓储子系统会将可出仓手机数量减少，同时通知采购管理子系统当前销售订单；仓储子系统的库存到达阈值以下，会通知销售子系统和采购子系统，并督促采购子系统采购；采购完成后，采购人员会把采购信息填入采购子系统，采购子系统会通知销售子系统采购完成，并通知仓库子系统增加库存。1、定义了colleague类，子系统都是通过继承该子类来实现，在该类初始化时，传入mediator者；2、分别定义了purchaseColleague、warehoustColleague和salesColleague三个类，分别表示采购子系统，仓库子系统和销售子系统，在purchaseColleague中的buyStuff、salesColleague的sellStuff方法，都是在接收到请求处理时调用了mediator的方法处理；在warehoustColleague仓储子系统类中，每次调用inc，dec方法，都是先判断保存的total、threshold值是否在要求范围内，当total数量小于threshold时，会通过调用mediator来通知采购子系统，当total数量增加时，通知销售子系统仓储数量增加；3、通过定义abstractMediator来保存三个子系统的实例，stockMediator通过继承abstractMediator类，实现execute方法，来实现三个子系统在调用过程中的逻辑处理，以此来完成通信。

代码运行结果如下:

PURCHASE:Bought 300MEDIATOR:Get Info -- buyWAREHOUSE:Increase 300MEDIATOR:Get Info -- increaseSALES:Get Notice -- Inc 300PURCHASE:Get Notice -- Inc 300SALES:Get Notice -- Bought 300SALES:Sell 120MEDIATOR:Get Info -- sellWAREHOUSE:Decrease 120MEDIATOR:Get Info -- decreaseSALES:Get Notice -- Dec 120PURCHASE:Get Notice -- Dec 120WARNING:Warning ... Stock is low ..MEDIATOR:Get Info -- warningSALES:Get Notice -- Stock is low 180 leftPURCHASE:Get Notice -- Stock is low. Please Buy More 180PURCHASE:Get Notice -- Sold 120

中介者模式应用场景:

1、设计类图时，出现了网状结构时，可以考虑将类图设计成星型结构，这样就可以实现中介模式；2、适用于一组对象以定义良好但是复杂的方式进行通信的场合；3、想定制一个分布在多个类中的行为，而又不想生成太多的子类的场合。

优缺点分析

优点

1、减少类与类的依赖，降低了类和类之间的耦合；2、容易扩展规模。

缺点

1、当处理逻辑较多时，会造成中介者本身的复杂性较大。