我使用SQL炼金术这样有一个简单的多对多的关系:瓶SQLAlchemy的多对多的关系只能通过关系名访问时返回一个结果
file_favorites = db.Table('file_favorites',
db.Column('file_id', db.Integer(), db.ForeignKey('file.id')),
db.Column('user_id', db.Integer(), db.ForeignKey('user.id')),
db.Column('created_at', db.DateTime(), default=db.func.now()))
class File(db.Model, helpers.ModelMixin):
id = db.Column(db.Integer, primary_key=True, autoincrement=True)
name = db.Column(db.Unicode, nullable=False)
description = db.Column(db.Unicode, nullable=False)
created_at = db.Column(db.DateTime(), default=func.now())
last_updated = db.Column(db.DateTime(), default=func.now(), onupdate=func.now())
user_id = db.Column('user_id', db.Integer(), db.ForeignKey('user.id'), nullable=False, index=True)
user = db.relationship('User')
favorited_by = db.relationship('User', secondary=file_favorites, lazy='dynamic')
def is_favorite_of(self, user):
query = File.query
query = query.join(file_favorites)
query = query.filter(file_favorites.c.file_id == self.id)
query = query.filter(file_favorites.c.user_id == user.id)
return query.count() > 0
def favorite(self, user):
if not self.is_favorite_of(user):
self.favorited_by.append(user)
def unfavorite(self, user):
if self.is_favorite_of(user):
self.favorited_by.remove(user)
我期望访问favorited_by属性将导致试图返回已收藏此文件的用户列表的查询。但是,似乎查询只访问FIRST用户收藏此文件。我对此感到困惑,并期望我不能正确理解sqlalchemy关系。下面是结果我遇到:
def create_model(model_class, *args, **kwargs):
model = model_class(*args, **kwargs)
db.session.add(model)
db.session.commit()
return model
def test_favorited_by(self):
user = create_model(User, username='user', email='[email protected]', password='password')
user1 = create_model(User, username='user1', email='[email protected]', password='password')
user2 = create_model(User, username='user2', email='[email protected]', password='password')
file = create_model(File, name='file', description='a description', user=user)
file.favorite(user1)
file.favorite(user)
file.favorite(user2)
db.session.commit()
print file.favorited_by
结果在此查询:
SELECT "user".id AS user_id, "user".email AS user_email, "user".username AS user_username, "user".password AS user_password, "user".active AS user_active, "user".last_login_at AS user_last_login_at, "user".current_login_at AS user_current_login_at, "user".last_login_ip AS user_last_login_ip, "user".current_login_ip AS user_current_login_ip, "user".login_count AS user_login_count, "user".last_updated AS user_last_updated, "user".created_at AS user_created_at
FROM "user", file_favorites
WHERE :param_1 = file_favorites.file_id AND "user".id = file_favorites.user_id
最终返回USER1,如果订单被切换,第一用户收藏该文件将永远是用户返回。
会发生什么事,如果你打印'file.favorited_by.all()'? – dirn 2014-12-02 21:08:20
打印file.favorited_by.all()返回: [] 列表中的单个用户对象,它与user1匹配,第一个用户将其设置为favorite。 –
elUser
2014-12-02 21:10:03
什么'File.favorite'看起来像?我的猜测是它正在做'self.favorited_by = user'而不是'self.favorited_by.append(user)'。 – dirn 2014-12-02 21:14:52