SQLAlchemy ManyToMany secondary table with additional fields
You will have to switch from using a plain, many-to-many relationship to using an "Association Object", which is basically just taking the association table and giving it a proper class mapping. You'll then define one-to-many relationships to User
and Community
:
class Membership(db.Model):
__tablename__ = 'community_members'
id = db.Column('id', db.Integer, primary_key=True)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
community_id = db.Column(db.Integer, db.ForeignKey('community.id'))
time_create = db.Column(db.DateTime, nullable=False, default=func.now())
community = db.relationship(Community, backref="memberships")
user = db.relationship(User, backref="memberships")
class Community(db.Model):
__tablename__ = 'community'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(100), nullable=False, unique=True)
But you may only occasionally be interested in the create time; you want the old relationship back! well, you don't want to set up the relationship
twice; because sqlalchemy will think that you somehow want two associations; which must mean something different! You can do this by adding in an association proxy.
from sqlalchemy.ext.associationproxy import association_proxy
Community.members = association_proxy("memberships", "user")
User.communities = association_proxy("memberships", "community")