CODEWITHSUNDEEP
pythonflasksqlalchemy
hasdrubal
hasdrubal

Reputation: 1148

Attribute error for Association Proxy in SQLAlchemy

I try to use the association proxy of the SQLAlchemy toolbox. These are the two concerning models, mapped for a one-to-many relation:

class User(object):
    query = db_session.query_property()
    def __init__(self, id):
        self.id = id
    def __repr__(self):
        return '{\"id: \"%i}' % (self.id)

class Context(object):
    query = db_session.query_property()
    def __init__(self, name, user, description=None, private=False):
        self.name = name
        self.description = description
        self.private = private
        self.user_id = user
    def __repr__(self):
        return '{\"id\": %i,\"name\":\"%s\", \"description\":\"%s\", \"private\":\"%r\" }' \
        % (self.id, self.name, self.description, self.private)

users = Table('users', metadata, 
    Column('id',Integer, primary_key=True))   
    mapper(User, users, properties={
'contexts' : relationship(Context, backref='user', lazy='dynamic')
})

contexts = Table('contexts', metadata, 
    Column('id', Integer, primary_key=True), 
    Column('name', String(50), nullable=True), 
    Column('description', String(255)), 
    Column('private', Boolean, default=True), 
    Column('user_id', Integer, ForeignKey('users.id'), nullable=False),
    UniqueConstraint('name', 'user_id','private')) 
mapper(Context, contexts)})

For querying I use the following:

user = User.query.filter(User.id==id)
for context in user.contexts:
   context.do_stuff()

But the following error appears:

AttributeError: 'Query' object has no attribute 'contexts'

Upvotes: 0

Views: 1112

Answers (1)

van
van

Reputation: 77072

The cause of the problem is the lazy='dynamic' on your relationship, which returns a Query object (so that additional operations like filtering/ordering etc) can be performed. To solve this, just call all():

user = User.query.filter(User.id==id)
for context in user.contexts.all():
   context.do_stuff()

Upvotes: 1

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