python 设计模式初级

面向对象

设计模式

===

1. 简单工厂模式

   设计一个商品类和苹果手机类，同时设计一个苹果手机专卖店类。苹果手机专卖店类可以下订单和出售手机。运行效果

    ip=IphoneShop()
   
    ip.order()
    ip.order()
    ip.order()
    
    print('库存中共有:',IphoneShop.iphone_count,'台手机')
    
    ip.sail()
    ip.sail()
    ip.sail()
    ip.sail()
    
    运行结果：
        iphone X 正在出库
        iphone X 正在出库
        iphone X 正在出库
        库存中共有: 3 台手机
        售出一台手机，库存还有2台手机
        售出一台手机，库存还有1台手机
        售出一台手机，库存还有0台手机
        手机已经售完！！请进货
   

   代码如下

    class Goods(object):
        def __init__(self,brand,price):
            self.price=price
            self.brand=brand
        def outGoods(self):
            print(self.brand,'正在出库')
    
    class Iphone(Goods):
        def __init__(self,brand,price,name):
            super(Iphone, self).__init__(brand,price)
            self.name=name
            print(self.name, '正在出库')
        def outGoods(self):
            print(self.name,'正在出库')
    class Sasung(Goods):
        def __init__(self,brand,price,name,pencil):
            super(Sasung, self).__init__(brand,price)
            self.name=name
            self.pencil=pencil
            print(self.name, '正在出库')
        def outGoods(self):
            print(self.name,'正在出库')
    
    def createMobile(brand):
        if brand=='apple':
            return Iphone('apple',5600,'iphone X')
        elif brand=='sasung':
            return Sasung('sasung',4600,'galaxy s6','black pencil')
    
    class IphoneShop(object):
        iphone_count = 0
        def __init__(self):
            self.iphone_count = 0
        def order(self):
            IphoneShop.iphone_count += 1
            return createMobile('apple')
    
        def sail(self):
            if IphoneShop.iphone_count>0:
                IphoneShop.iphone_count -= 1
                print('售出一台手机，库存还有{0}台手机'.format(IphoneShop.iphone_count))
            else:
                print('手机已经售完！！请进货')
    ip=IphoneShop()
    
    ip.order()
    ip.order()
    ip.order()
    
    print('库存中共有:',IphoneShop.iphone_count,'台手机')
    
    ip.sail()
    ip.sail()
    ip.sail()
    ip.sail()
   

   工厂模式：

    class Goods(object):
        def __init__(self,brand,price):
            self.price=price
            self.brand=brand
        def outGoods(self):
            print(self.brand,'正在出库')
    
    class Iphone(Goods):
        def __init__(self,brand,price,name):
            super(Iphone, self).__init__(brand,price)
            self.name=name
            print(self.name, '正在出库')
    class Sasung(Goods):
        def __init__(self,brand,price,name,pencil):
            super(Sasung, self).__init__(brand,price)
            self.name=name
            self.pencil=pencil
            print(self.name, '正在出库')
    
    
    # def createMobile(brand):
    #     if brand=='apple':
    #         return Iphone('apple',5600,'iphone X')
    #     elif brand=='sasung':
    #         return Sasung('sasung',4600,'galaxy s6','black pencil')
    
    
    class MobileFactory(object):
        def createMobile(self,brand):
            if brand=='apple':
                return Iphone('apple',5600,'iphone X')
            elif brand=='sasung':
                return Sasung('sasung',4600,'galaxy s6','black pencil')
    class Shop(object):
        iphone_count = 0
        def __init__(self):
            self.factory=MobileFactory()
        def order(self,brand):
            IphoneShop.iphone_count += 1
            return self.factory.createMobile(brand)
    
        def sail(self):
            if IphoneShop.iphone_count>0:
                IphoneShop.iphone_count -= 1
                print('售出一台手机，库存还有{0}台手机'.format(IphoneShop.iphone_count))
            else:
                print('手机已经售完！！请进货')
    ip=Shop()
    
    ip.order('apple')
    ip.order('sasung')
    ip.order('apple')
    
    print('库存中共有:',IphoneShop.iphone_count,'台手机')
    
    ip.sail()
    ip.sail()
    ip.sail()
    ip.sail()
   

2. 工厂方法模式
   简单工厂模式中MobileFactory对象由Shop类初始化来创建，这就决定了Shop只能创建MobileFactory对象。我们把MobileFactory对象交给Shop子类来创建，这样就扩展了Shop的功能。如下：

    class Shop(object):
        def createGoods(self,brand):
            pass
        def order(self,brand):
            pass
        def sail(self):
            pass
    
    class MobileShop(Shop):
        Mobile_count=0
        def createGoods(self,brand):
            MobileShop.Mobile_count +=1
            return MobileFactory().createMobile(brand)
        def order(self,brand):
            mobile=self.createGoods(brand)
            print(mobile.name,'手机到货，库存为', MobileShop.Mobile_count)
            return mobile
        def sail(self):
            if MobileShop.Mobile_count>0:
                MobileShop.Mobile_count -= 1
                print('售出一台手机，库存还有{0}台手机'.format(MobileShop.Mobile_count))
            else:
                print('手机已经售完！！请进货')
    ip=MobileShop()
    
    ip.order('apple')
    ip.order('sasung')
    ip.order('apple')
    
    
    
    ip.sail()
    ip.sail()
    ip.sail()
    ip.sail()
   

3. 单例模式预备 new

   __new__()必须要有返回值，返回实例化出来的实例，需要注意的是，可以return父类__new__()出来的实例，也可以直接将object的__new__()出来的实例返回。

   init()有一个参数self，该self参数就是new()返回的实例，init()在new()的基础上可以完成一些其它初始化的动作，init()不需要返回值。

   若new()没有正确返回当前类cls的实例，那init()将不会被调用，即使是父类的实例也不行

   我们可以将类比作制造商，new()方法就是前期的原材料购买环节，init()方法就是在有原材料的基础上，加工，初始化商品环节。

    class A(object):
        def __new__(cls, name,age):
            print('new')
            return object.__new__(cls)
    
        def __init__(self,name,age):
            self.name=name
            self.age=age
    a1=A('tom',12)
    a2=A('tt',16)
    a3=A('ff',16)
   

4. 单例模式

    class A(object):
        __instance=None
        __first=False
        def __new__(cls, name,age):
            if not cls.__instance:
                cls.__instance=object.__new__(cls)
    
            return  cls.__instance
    
        def __init__(self,name,age):
            if not A.__first:
                self.name=name
                self.age=age
                A.__first=True
    a1=A('tom',12)
    a2=A('tt',16)
    a3=A('ff',16)
    
    print(id(a1))