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我正在尝试通过使用 mongoengine 定位列表项的 _id 从 ListField 中删除一个项目 - 我在这里指的是关于原子更新的 mongoengine 文档：http: //docs.mongoengine.org/guide/querying.html#atomic -更新

模型

class Prospect(db.Document):
  comments          = db.ListField(db.EmbeddedDocumentField('Comment'))

class Comment(db.EmbeddedDocument):
  _id             = db.ObjectIdField(default=bson.ObjectId())
  created_at      = db.DateTimeField(default=datetime.datetime.now, required=True)
  body            = db.StringField(verbose_name="Note", required=True)
  author          = db.StringField(verbose_name="Name", max_length=255, required=True)

Mongo 文档如下所示：

...
"comments": [
      {
        "_id": {
            "$oid": "53bebb55c3b5a0db7829c15f"
        },
        "created_at": {
            "$date": "2014-07-09T18:26:58.444Z"
        },
        "body": "Did something\n",
        "author": "Dave Roma"
    },

我试图删除这样的评论：

prospect = Prospect.objects(id=request.form['prospect_id']).update_one(pull___id=request.form['comment_id'])

我收到一个 mongoengine invalidQueryError：

InvalidQueryError: Cannot resolve field "_id"
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1 回答 1

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您的问题的答案将是：

prospect = Prospect.objects(id=request.form['prospect_id']).update_one(pull__comments__id=request.form['comment_id'])

您的原始查询试图_id在 mongoengine 中查找显然不存在的字段。

现在解决您在评论中谈到的问题。

解决方案1：

class Prospect(db.Document):
    comments = db.ListField(db.EmbeddedDocumentField('Comment'))

    def get_next_comment_id(self):
        return len(self.comments)+1

    def add_new_comment(self, author, body):
        self.update(add_to_set__comments=Comment(_id=self.get_next_comment_id(), author=author, body=body)

class Comment(db.EmbeddedDocument):
  _id             = db.IntField(required=True)
  created_at      = db.DateTimeField(default=datetime.datetime.now, required=True)
  body            = db.StringField(verbose_name="Note", required=True)
  author          = db.StringField(verbose_name="Name", max_length=255, required=True)

如果两个客户端同时尝试添加新帖子，上述解决方案可能会失败。他们可能有相同的_id。无法在 mongo 中的嵌入文档字段中强制执行唯一性。您只能使用客户端代码执行此操作。

解决方案2：

制作单独的评论集。

class Prospect(db.Document):
    comments = db.ListField(db.EmbeddedDocumentField('Comment'))

class Comment(db.Document):
  on_prospect     = db.ReferenceField(Prospect)
  created_at      = db.DateTimeField(default=datetime.datetime.now, required=True)
  body            = db.StringField(verbose_name="Note", required=True)
  author          = db.StringField(verbose_name="Name", max_length=255, required=True)

def add_new_comment(prospect, author, body):
    comment = Comment(on_prospect = prospect, author=author, body=body).save()
    return comment.id

def get_all_posts_on_prospect(prospect):
    return Comment.objects(on_prospect = prospect).order_by('-id')

这是每个评论的唯一 ID。

解决方案3：

这只是一个想法，我不确定利弊。

class Prospect(db.Document):
    comments = db.ListField(db.EmbeddedDocumentField('Comment'))

    def get_id_for_comment(self, comment):
        return self.comments.index(comment)

class Comment(db.EmbeddedDocument):
  _id             = db.IntField()
  created_at      = db.DateTimeField(default=datetime.datetime.now, required=True)
  body            = db.StringField(verbose_name="Note", required=True)
  author          = db.StringField(verbose_name="Name", max_length=255, required=True)

def add_new_comment(prospect, author, body)
    comment = Comment(_id=self.get_next_comment_id(), author=author, body=body)
    prospect.update(add_to_set__comments = comment)
    cid = prospect.get_id_for_comment(comment)
    prospect.update(set__comments__cid__id = cid)
    return cid
于 2014-07-24T00:04:47.703 回答