我试图在从 MongoDB 数据库查询时将 ObjectId 和 ISODate 转换为字符串表示形式。

def mongo_to_dict(obj, exclude_fields):
    return_data = []

    if obj is None:
        return None

    if isinstance(obj, Document):
        return_data.append(("_id", str(obj.id)))

    for field_name in obj._fields:

        if field_name in exclude_fields:
            continue

        if field_name in ("id",):
            continue

        data = obj._data[field_name]

        if isinstance(obj._fields[field_name], ListField):
            return_data.append((field_name, list_field_to_dict(data)))
        elif isinstance(obj._fields[field_name], EmbeddedDocumentField):
            return_data.append((field_name, mongo_to_dict(data, [])))
        elif isinstance(obj._fields[field_name], DictField):
            return_data.append((field_name, data))
        else:
            return_data.append((field_name, mongo_to_python_type(obj._fields[field_name], data)))

    return dict(return_data)


def list_field_to_dict(list_field):
    return_data = []

    for item in list_field:
        if isinstance(item, EmbeddedDocument):
            return_data.append(mongo_to_dict(item, []))
        else:
            return_data.append(mongo_to_python_type(item, item))

    return return_data


def mongo_to_python_type(field, data):
    if isinstance(field, DateTimeField):
        return time.mktime(data.timetuple()) * 1000
    elif isinstance(field, ComplexDateTimeField):
        return field.to_python(data).isoformat()
    elif isinstance(field, StringField):
        return str(data)
    elif isinstance(field, FloatField):
        return float(data)
    elif isinstance(field, IntField):
        return int(data)
    elif isinstance(field, BooleanField):
        return bool(data)
    elif isinstance(field, ObjectIdField):
        return str(data)
    elif isinstance(field, DecimalField):
        return data
    else:
        return str(data)


class Portfolio(Document):
    meta = {'collection': 'Portfolios'}
    PortfolioName = StringField()
    LastUpdateDate = DateTimeField(default=datetime.datetime.now())
    RecentActivity = ListField(default=[])


    def to_dict(self):
        return mongo_to_dict(self, [])

现在当我像这样创建投资组合对象时

a = Portfolio(PortfolioName='BB Visa').save()

当我尝试为 a.to_dict() 之类的对象获取 to_dict() 表示时，它工作得很好。

{'_id': '5581cf9129e457241a32e8f7', 'PortfolioName': 'BB Visa', 'RecentActivity': [], 'LastUpdateDate': 1434570641000.0}

但问题是我希望 to_dict() 在类级别而不是对象级别上操作。

所以当我尝试像这样定义一个自定义查询集时

class Portfolio(Document):
    meta = {'collection': 'Portfolios'}
    PortfolioName = StringField()
    LastUpdateDate = DateTimeField(default=datetime.datetime.now())
    RecentActivity = ListField(default=[])

    @queryset_manager
    def to_dict(self, queryset):
        return mongo_to_dict(self, [])

现在运行以下命令 Portfolio.to_dict() 会生成如下错误 追溯(最近一次通话最后一次):

  File "/home/ajay/PycharmProjects/solveit/test.py", line 102, in <module>
    print(Portfolio.to_dict())
  File "/home/ajay/.pyenv/versions/3.4.3/lib/python3.4/site-packages/mongoengine/queryset/manager.py", line 43, in __get__
    queryset = self.get_queryset(owner, queryset)
  File "/home/ajay/PycharmProjects/solveit/test.py", line 83, in to_dict
    return mongo_to_dict(self, [])
  File "/home/ajay/PycharmProjects/solveit/test.py", line 28, in mongo_to_dict
    data = obj._data[field_name]
TypeError: 'member_descriptor' object is not subscriptable

我知道 QuerySet 管理器将类传递给函数，这就是错误的原因。如何解决这个问题。

最佳答案

实际上我不确定将其定义为 @queryset_manager 是否正确，因为根据 documentation

mongoengine.queryset.queryset_manager(func) Decorator that allows you to define custom QuerySet managers on Document classes. The manager must be a function that accepts a Document class as its first argument, and a QuerySet as its second argument. The method function should return a QuerySet, probably the same one that was passed in, but modified in some way.

我建议添加一些单独的 utils 函数来获取查询集:

def convert_queryset_to_list_of_dicts(queryset):
    return [mongo_to_dict(obj) for obj in queryset]

或者如果你仍然想将它作为 @queryset_manager 那么:

...
@queryset_manager
def to_dict(self, queryset):
    return [mongo_to_dict(obj) for obj in queryset]
...

还有一个现成的mongoengine模型对象方法to_mongo。您可以这样尝试:[obj.to_mongo() for obj in queryset]。不适用吗？

关于python - Mongoengine 自定义查询集，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30901274/