Question

如何覆盖继承的类方法，需要查询子类的特定属性？

我不确定该怎么做。这就是我所拥有的：

    class base_class:

        @classmethod
        def a_method(cls, something):
            return ndb.Query(kind=cls.__name__).fetch(keys_only=True)

        @classmethod
            def calls_a_method(cls, size=1, soemthing):

                 entity_keys = cls.a_method(something)

    class child_class(base_class):

         a_property = ndb.BooleanProperty()

         def another_method():
             stuff =  child_class.calls_a_method() #?

如何覆盖base_class中的a_method，这样它也会过滤出child_class的a_property = False的键？

Answer 1

我认为如果你在方法中分解查询，可以在子类中构造一个自定义查询：

class base_class:

    @classmethod
    def a_method(cls, something):
        return ndb.Query(kind=cls.__name__)

    @classmethod
    def calls_a_method(cls, size=1, something):
        entity_keys = cls.a_method(something).fetch(keys_only=True)

class child_class(base_class):

    a_property = ndb.BooleanProperty()

    @classmethod
    def another_method(cls):
        q = cls.a_method(something).filter(cls.a_property == False)
        entity_keys = q.fetch(keys_only=True)

Answer 2

这样的事情怎么样？

    class base_class(ndb.Model):
            @classmethod
            def a_method(cls, something):
                    return cls.Query().fetch(keys_only=True)

            @classmethod
            def calls_a_method(cls, something):
                    entity_keys = cls.a_method(something)

    class child_class(base_class):
            a_property = ndb.BooleanProperty()

            @classmethod
            def another_method(cls, value):
                    return cls.calls_a_method(value)

            @classmethod
            def a_method(cls, something):
                    return cls.query(cls.a_property==something).fetch(keys_only=True)

python，gae，ndb，覆盖一个类方法，但它需要应用于实例吗？

2 个答案: