Many to many, Relation and SQLAlchemy association table

[nbx3]

I'm just trying out potion, i wanted to evaluate many to many options and found issue #26 which mentions a fix in an older version (im using 0.15.0). This however errors with

RuntimeError: Resource named "user" is not registered with the Api it is bound to.

Code example

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.orm import backref
from flask_potion.routes import Relation
from flask_potion import ModelResource, fields, Api

app = Flask(__name__)
db = SQLAlchemy(app)

roles_users = db.Table('roles_users',
                       db.Column(
                           'user_id',
                           db.Integer(),
                           db.ForeignKey('user.id')),
                       db.Column('role_id',
                                 db.Integer(),
                                 db.ForeignKey('role.id')))

class Role(db.Model):

    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))
    users = db.relationship('User', secondary=roles_users,
                           backref=db.backref('roles', lazy='dynamic'))


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    firstname = db.Column(db.String(), nullable=False)
    lastname = db.Column(db.String(), nullable=False)

db.create_all()

class RoleResource(ModelResource):
    users = Relation('user')
    class Meta:
        model = Role

class UserResource(ModelResource):

    class Meta:
        model = User

api = Api(app)
api.add_resource(RoleResource)
api.add_resource(UserResource)

if __name__ == '__main__':
    app.run()

[lyschoening]

Could you try adding the UserResource before adding the RoleResource? For most uses, the Relation() property is unnecessary. I encourage using ToOne fields and filtering on those instead.

https://potion.readthedocs.io/en/latest/quickstart.html#relationships