你能解释一下,如何实现AFactory
类这样做。看来我需要使用元类但是怎么样?我所有的尝试都失败了KeyError
dct = {
'key1': 'value1',
'key2': 'value2'
}
class AFactory:
pass
class A:
NAME = ''
VARIABLE = dct[NAME]
A1 = AFactory('key1')
a1 = A1()
assert a1.NAME == 'key1'
assert a1.VARIABLE == 'value1'
A2 = AFactory('key2')
a2 = A2()
assert a2.NAME == 'key2'
assert a2.VARIABLE == 'value2'
听起来你真的想要一个班级工厂,而不是一个元类。 (是的,元类也是类工厂,但它们不是唯一的。)所以最简单的解决方案是将AFactory
定义为函数:
def AFactory(name):
class A:
NAME = name
VARIABLE = dct[NAME]
return A
如果你真的需要一个元类,你should implement an alternative constructor而不是试图使元类可以调用为AFactory(name)
:
class AFactory(type):
@classmethod
def make(mcs, name):
clsname = 'A'
bases = ()
attrs = {
'NAME': name,
'VARIABLE': dct[name]
}
return mcs(clsname, bases, attrs)
然后你可以使用它
A1 = AFactory.make('key1')