面向对象（三）

简单工厂模式

 

class CarStore(object):
    def order(self,car_type):
        return select_car_by_type(car_type)
def select_car_by_type(car_type):
    if car_type == "丰田":
        return TOYOTA()
    elif car_type =="本田":
        return HONDA()
    elif car_type =="尼桑":
        return NISSAN()
    else:
        pass
class Car(object):

    def move(self):
        print("车在移动")
    def stop(self):
        print("车已停止")
    def music(self):
        print("车播放音乐")

class TOYOTA(Car):
    def __str__(self):
        return "这款车是丰田牌轿车！"
class HONDA(Car):
    def __str__(self):
        return "这款车是本田牌轿车！"
class NISSAN(Car):
    def __str__(self):
        return "这款车是尼桑牌轿车！"
car_store = CarStore()
car = car_store.order("丰田")
print(car)

 

class CarStore(object):
    def __init__(self):
        self.factory = Factory()
    def order(self,car_type):
        return self.factory.select_car_by_type(car_type)

class Factory(object):
    def select_car_by_type(self,car_type):
        if car_type == "丰田":
            return TOYOTA()
        elif car_type =="本田":
            return HONDA()
        elif car_type =="尼桑":
            return NISSAN()
        else:
            pass
class Car(object):

    def move(self):
        print("车在移动")
    def stop(self):
        print("车已停止")
    def music(self):
        print("车播放音乐")

class TOYOTA(Car):
    def __str__(self):
        return "这款车是丰田牌轿车！"
class HONDA(Car):
    def __str__(self):
        return "这款车是本田牌轿车！"
class NISSAN(Car):
    def __str__(self):
        return "这款车是尼桑牌轿车！"
car_store = CarStore()
car = car_store.order("丰田")
print(car)
car.move()

 

 

工厂方法模式：

 

 

 

__new__ 方法：

class Dog(object):
    def __init__(self):
        print("---init方法---")
    def __del__(self):
        print("---del方法---")
        
    def __str__(self):
        print("---str方法---")
        return "返回对象的描述信息"
    def __new__(cls):     #cls是Dog指向的那个类对象
        #print(id(cls))
        print("---new方法---")
        return object.__new__(cls)
#print(id(Dog))
xtq = Dog()
print(xtq)


---new方法---
---init方法---
---str方法---
返回对象的描述信息
---del方法---

 

只初始化一次对象

class Dog(object):
    __instance = None   #空
    __init__flag = False
    def __new__(cls,name):
        if cls.__instance == None:
            cls.__instance = object.__new__(cls)
            return cls.__instance
        else:
            return cls.__instance
    def __init__(self,name):
        if self.__init__flag ==False:
            self.name = name
            self.__init__flag = True
        
a = Dog("旺财")
print(id(a))
print(a.name)
b = Dog("笑天犬")
print(id(b))
print(b.name)