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概述：

我的用户文档引用了带有 FileFields 的图像文档。您不能使用 FileField 对对象进行深度复制（为什么不呢？）。深度复制用户文档会取消引用关联的图像（使用 FileField），因此会失败。

我正在尝试使用 MongoEngine (0.7.8) 查询一个集合，如果我这样查询：

    >>> cls.objects(Q(author=devin_user))
    [<FollowUserEvent: [<User: Devin> => <User: Strike>]>]
    # Querying author works fine

    >>> cls.objects(Q(parent=strike_user))
    [<FollowUserEvent: [<User: Devin> => <User: Strike>]>]
    # Querying parent works fine

    >>> cls.objects(Q(parent=strike_user) & Q(author=devin_user))
    *** TypeError: 'Collection' object is not callable. If you meant to call the '__deepcopy__' method on a 'Collection' object it is failing because no such method exists.
    # Definitely fails here, but why?


    # Even stranger, if I combine a query on parent and hidden_at it succeeds, but if I combine a query on author and hidden_at it gloriously fails
    >>> cls.objects(Q(parent=strike_user) & Q(hidden_at=None))
    [<FollowUserEvent: [<User: Devin> => <User: Strike>]>]
    # Querying parent works fine

    >>> cls.objects(Q(author=devin_user) & Q(hidden_at=None))
    *** TypeError: 'Collection' object is not callable. If you meant to call the '__deepcopy__' method on a 'Collection' object it is failing because no such method exists.
    # Boom!

stroke_user 和 devin_user 是两个用户文档。这是 Event 的样子（顺便说一下，它确实允许继承）。

    class Event(Document):                                             
       """                                                            
       :param anti: tells if an event is related to an inverse event  
           e.g. follow/unfollow, favorite/unfavorite                  
       :param partner: relates an anti-event to an event.             
           only set on the undoing event                              
       """                                                            
       author = GenericReferenceField(required=True)                  
       parent = GenericReferenceField(required=True)                  
       created_at = DateTimeField(required=True, default=datetime.now)
       hidden_at = DateTimeField()                                    

       anti = BooleanField(default=False)                             
       partner = ReferenceField('Event', dbref=False)                 
       meta = {                                                       
           'cascade': False,                                          
           'allow_inheritance': True }

       def __repr__(self):
           action = "=/>" if self.anti else "=>"
           return "<%s: [%s %s %s]>" % (self.__class__.__name__,
               self.author.__repr__(), action, self.parent.__repr__())

对我来说似乎是一个错误，但我很想听到反馈:)

更新：

似乎 mongoengine/queryset.py:98 调用了 copy.deepcopy。这遵循一个 ReferenceField，并尝试复制它的 FileField 数据。不幸的是，这不起作用。

    Class Image(Document):
        file = FileField(required=True)

    Class User(Document):
        name = StringField()
        image = ReferenceField('Image')

    >>> copy.deepcopy(user)
    *** TypeError: 'Collection' object is not callable. If ...

    >>> user.image = None
    >>> copy.deepcopy(user)
    <User: Devin>
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1 回答 1

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事实证明，这是一个错误！我在概述中所说的是正确的。[错误状态

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于 2012-12-17T19:34:27.303 回答