面向对象-单例模式实现的五种方式-21

刺骨的言语ヽ痛彻心扉 2021-12-19 15:49 270阅读 0赞

[面向对象-单例模式实现的五种方式-21][-_-21]

## 一、classmethod装饰器 ##

ip = '192.168.13.98'
    port = '3306'
    
    
    class MySQL:
        __instance = None
    
        def __init__(self, ip, port):
            self.ip = ip
            self.port = port
    
        @classmethod
        def instance(cls, *args, **kwargs):
            if args or kwargs:
                cls.__instance = cls(*args, **kwargs)
            return cls.__instance
    
    
    obj1 = MySQL.instance(ip, port)
    obj2 = MySQL.instance()
    obj3 = MySQL.instance()
    print(obj1)
    print(obj2, obj2.__dict__)
    print(obj3, obj3.__dict__)

输出结果  
`<main.MySQL object at 0x058D6F30>`  
`<main.MySQL object at 0x058D6F30> {'ip': '192.168.13.98', 'port': '3306'}`  
`<main.MySQL object at 0x058D6F30> {'ip': '192.168.13.98', 'port': '3306'}`  
  
**二、类的装饰器**

def singlegon(cls):
        _instance = cls(ip, port)
    
        def wrapper(*args, **kwargs):
            if args or kwargs:
                return cls(*args, **kwargs)
            return _instance
    
        return wrapper
    
    
    @singlegon
    class MySQL1:
        def __init__(self, ip, port):
            self.ip = ip
            self.port = port
    
    
    obj1 = MySQL1()
    obj2 = MySQL1()
    obj3 = MySQL1('1.1.1.3', 8080)
    print(obj1)
    print(obj2, obj2.__dict__)
    print(obj3, obj3.__dict__)

运行结果  
`<main.MySQL1 object at 0x04C102B0>`  
`<main.MySQL1 object at 0x04C102B0> {'ip': '192.168.13.98', 'port': '3306'}`  
`<main.MySQL1 object at 0x04C10310> {'ip': '1.1.1.3', 'port': 8080}`  
  
**三、元类**

class Mymetaclass(type):
        def __init__(self, class_name, class_bases, class_dic):
            super().__init__(class_name, class_bases, class_dic)
            self.__instance = self(ip, port)
    
        def __call__(self, *args, **kwargs):
            if args or kwargs:
                obj = self.__new__(self)
                self.__init__(obj, *args, **kwargs)
                self.__instance = obj
            return self.__instance
    
    
    class MySQL2(metaclass=Mymetaclass):
        def __init__(self, ip, port):
            self.ip = ip
            self.port = port
    
    
    obj1 = MySQL2()
    obj2 = MySQL2()
    obj3 = MySQL2('1.1.1.3', 80)
    print(obj1)
    print(obj2, obj2.__dict__)
    print(obj3, obj3.__dict__)

运行结果  
`<main.MySQL2 object at 0x04D003B0>`  
`<main.MySQL2 object at 0x04D003B0> {'ip': '192.168.13.98', 'port': '3306'}`  
`<main.MySQL2 object at 0x04D003D0> {'ip': '1.1.1.3', 'port': 80}`  
  
**四、模块导入**  
**instance.py**

class MySQL:
        def __init__(self, ip, port):
            self.ip = ip
            self.port = port
    
    
    ip = '192.168.13.98'
    port = 3306
    instance = MySQL(ip, port)

import os, sys
    
    sys.path.append(os.path.dirname(os.path.dirname(__file__)))
    from day30 import instance
    
    
    obj1 = instance.instance
    obj2 = instance.instance
    obj3 = instance.MySQL('1.1.1.3', 80)
    print(obj1)
    print(obj2, obj2.__dict__)
    print(obj3, obj3.__dict__)

运行结果  
`<day30.instance.MySQL object at 0x052B0AB0>`  
`<day30.instance.MySQL object at 0x052B0AB0> {'ip': '192.168.13.98', 'port': 3306}`  
`<day30.instance.MySQL object at 0x052B03F0> {'ip': '1.1.1.3', 'port': 80}`  
  
**五、重写\_\_new\_\_()**

class MySQL3(object):
        __instance = None
        __first_init = True
    
        def __init__(self, ip, port):
            if self.__first_init:
                self.ip = ip
                self.port = port
                self.__first_init = False
    
        def __new__(cls, *args, **kwargs):
            if not cls.__instance:
                cls.__instance = object.__new__(cls)
            return cls.__instance
    
    obj1 = MySQL3(ip, port)
    obj2 = MySQL3(ip, port)
    obj3 = MySQL3('1.1.1.3', 80)
    print(obj1)
    print(obj2, obj2.__dict__)
    print(obj3, obj3.__dict__)

运行结果  
`<main.MySQL3 object at 0x059603F0>`  
`<main.MySQL3 object at 0x059603F0> {'ip': '192.168.13.98', 'port': '3306', '_MySQL3__first_init': False}`  
`<main.MySQL3 object at 0x059603F0> {'ip': '192.168.13.98', 'port': '3306', '_MySQL3__first_init': False}`

posted on 2018-12-27 08:59 [漫天飞雪世情难却][Link 1] 阅读( ...) 评论( ...) [编辑][Link 2] 收藏

转载于:https://www.cnblogs.com/jokezl/articles/10183023.html

[-_-21]: https://www.cnblogs.com/jokezl/articles/10183023.html
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