（一）Python入门-6面向对象编程：12设计模式之工厂模式-单例模式

#工厂模式实现
class CarFactory:
    def creatCar(self,brand):
        if brand == ‘奔驰‘:
            return Benz()
        elif brand == ‘宝马‘:
            return BMW()
        elif brand == ‘比亚迪‘:
            return BYD()
        else:
            return ‘位置品牌，无法创建‘
class Benz:
    pass
class BMW:
    pass
class BYD:
    pass

factory = CarFactory()
c1 = factory.creatCar(‘奔驰‘)
c2 = factory.creatCar(‘宝马‘)
print(c1)
print(c2)

#单例模式实现
class MySingleton:
    __obj = None     #用于判断对象是否已经创建，保证只创建一个对象
    __init_flag = True   #用于判断是否已进行初始化，保证只初始化一次

    def __new__(cls, *args, **kwargs):
        if cls.__obj == None:    #判断是否已创建对象，为None说明没有对象，进行创建，否则对象已有不再创建
            cls.__obj = object.__new__(cls)
        return cls.__obj

    def __init__(self,name):
        if MySingleton.__init_flag:   #判断是否初始化，True未初始化，进行初始化操作
            print(‘init...‘)
            self.name = name
            MySingleton.__init_flag = False   #初始化标记设为False，保证只初始化一次

a = MySingleton(‘aa‘)
print(a)
b = MySingleton(‘bb‘)
print(b)
c = MySingleton(‘cc‘)
print(c)

#测试工厂模式和单例模式的整合使用

class CarFactory:
    __obj = None
    __init_flag = True

    def creatCar(self,brand):
        if brand == ‘奔驰‘:
            return Benz()
        elif brand == ‘宝马‘:
            return BMW()
        elif brand == ‘比亚迪‘:
            return BYD()
        else:
            return ‘位置品牌，无法创建‘
        
    def __new__(cls, *args, **kwargs):
        if cls.__obj == None:
            cls.__obj = object.__new__(cls)
        return cls.__obj

    def __init__(self):
        if CarFactory.__init_flag:
            print(‘init CarFactory...‘)
            CarFactory.__init_flag = False

class Benz:
    pass
class BMW:
    pass
class BYD:
    pass

factory = CarFactory()
c1 = factory.creatCar(‘奔驰‘)
c2 = factory.creatCar(‘宝马‘)
print(c1)
print(c2)

factory2 = CarFactory()
print(factory,factory2)