什麼是元類,請用代碼解釋如何使用元類
'''
metaclass: 元類,類似於創建類的模板,所有的類都是通過他來創建的,可以自由控制類的創建過程
單例模式、ORM模式
'''
class SingLeton(type):
def __init__(self, *args, **kwargs):
print('in __init__')
self.__instance = None
super(SingLeton, self).__init__(*args, **kwargs)
def __call__(self, *args, **kwargs):
print('in __call__')
if self.__instance == None:
self.__instance = super(SingLeton, self).__call__(*args, **kwargs)
print(type(self.__instance))
return self.__instance
class MyClass(metaclass=SingLeton):
pass
my1 = MyClass()
my2 = MyClass()
print(my1 is my2)
in __init__
in __call__
<class '__main__.MyClass'>
in __call__
True
持續更新中。。。。