SQLAlchemy混合屬性無法正常工作

Question

我有一個模型的幾何點列，所以我想定義setter來接收緯度/經度，而不是創建的WKTElement。這裏是我的模型目前是這樣的：

class Poi(db.Model): 
    __tablename__ = 'api_pois' 

    id = db.Column(db.Integer, primary_key=True, unique=True) 
    name = db.Column(db.String(80), nullable=False) 
    user_id = db.Column(db.Integer, db.ForeignKey('api_users.id')) 
    creation_time = db.Column(db.DateTime, default=func.now()) 
    category_id = db.Column(db.Integer(), db.ForeignKey('api_poi_categories.id')) 
    category = db.relationship('PoiCategory') 
    geom = db.Column(Geometry('POINT', srid=4326), nullable=False) 
    metadata_poi = db.Column('metadata_poi') 

    def __init__(self, name, lat, lng, user_id=None, category_id=None, metadata_poi=None): 
     geom_str = 'POINT({} {})'.format(lng, lat) 
     self.name = name 
     self.user_id = user_id 
     self.category_id = category_id 
     self._geom = WKTElement(geom_str, srid=4326) 
     self.metadata_poi = metadata_poi 

    def __repr__(self): 
     return '<Poi %r %r>' % (self.id, self.name) 

    def as_dict(self, route_id=None): 
     sequence = None 

     if route_id: 
      from sintrafico.models.route import routes_pois 

      result = db.session.query(routes_pois).filter_by(route_id=route_id, poi_id=self.id). \ 
       order_by(routes_pois.c._sequence).one_or_none() 

      if result: 
       sequence = result[2] 

     geom = db.session.query(Poi, func.ST_X(self.geom), func.ST_Y(self.geom)).filter(Poi.id == self.id).one_or_none() 

     return { 
      'id': self.id, 
      'name': self.name if not sequence else '%s - %s' % (sequence, self.name), 
      'lat': geom[2], 
      'lon': geom[1], 
      'city': str(City.city_for_coord(geom[2], geom[1])), 
      'sequence': sequence if sequence else None, 
      'category_id': self.category_id, 
      'category': self.category.name, 
      'metadata': self.metadata_poi 
     } 

    @property 
    def location(self): 
     geom = db.session.query(Poi, func.ST_X(self.geom), func.ST_Y(self.geom)).filter(Poi.id == self.id).one_or_none() 
     return {'lat': geom[2], 'lon': geom[1]} 

    @hybrid_property 
    def geom(self): 
     return self._geom 

    @geom.setter 
    def geom(self, (lat, lng)): 
     geom_str = 'POINT({} {})'.format(lng, lat) 
     self._geom = WKTElement(geom_str, srid=4326) 

此代碼裏面as_dict()行geom = ...因爲POI對象不具有的屬性_geom它調用混合吸氣失敗。現在，如果我將線路更改爲

geom = db.session.query(Poi, func.ST_X(self._geom), func.ST_Y(self._geom)).filter(Poi.id == self.id).one_or_none() 

錯誤仍然存​​在，它只是移動到該行而不是setter。如果我改變聲明

_geom = db.Column(Geometry('POINT', srid=4326), nullable=False) 

然後我得到的錯誤是一個畸形的查詢：

HINT: Perhaps you meant to reference the column "api_pois.geom". 
[SQL: 'SELECT api_pois.id AS api_pois_id, api_pois.name AS api_pois_name, api_pois.user_id AS api_pois_user_id, api_pois.creation_time AS api_pois_creation_time, api_pois.category_id AS api_pois_category_id, ST_AsBinary(api_pois._geom) AS api_pois__geom, api_pois.metadata_poi AS api_pois_metadata_poi \nFROM api_pois \nWHERE api_pois.user_id = %(user_id_1)s ORDER BY api_pois.creation_time DESC'] [parameters: {'user_id_1': 1}] 

在這段代碼的最後一行：

if args['q']: 
    pois = pois.filter(func.lower(Poi.name).like('%{}%'.format(args['q'].lower()))) 

if args['categories'] is not None and len(args['categories']) > 0: 
    pois = [x for x in pois if x.category_id in args['categories']] 

我怎樣才能得到它上班？

Answer 1

名稱您的geom列明確，而不是讓聲明使用屬性名稱：

class Poi(db.Model): 
    ... 
    _geom = db.Column('geom', Geometry('POINT', srid=4326), nullable=False)