many-to-many with self

[Tim Shaffer]

I'm trying to figure out if it's possible to have a many-to-many relationship with self. Scenario is that users can have many managers and managers can manage many users.

First I tried this, which does not work (AttributeError: 'DeferredRelation' object has no attribute '_meta')

from peewee import SqliteDatabase

from peewee import CharField

from peewee import Model

from playhouse.fields import ManyToManyField

from playhouse.fields import DeferredRelation

db = SqliteDatabase(':memory:')

DeferredUser = DeferredRelation()

class User(Model):

name = CharField()

managed_users = ManyToManyField(DeferredUser)

class Meta:

database = db

DeferredUser.set_model(User)

User.create_table()

Anyway I can't see how that would work since it would try to create two "user_id" columns on the through model.

I can get it sort of working using an intermediary table and a property on the user. This doesn't get me the ability to "set" managed_users on a model instance like a ManyToMany field would.

class User(Model):

name = CharField()

class Meta:

database = db

@property

def managed_users(self):

return User.select() \

.join(ManagedUser, on=(ManagedUser.user_id == User.id)) \

.where(ManagedUser.manager_id == self.id)

class ManagedUser(Model):

manager = ForeignKeyField(User, related_name='manager_set')

user = ForeignKeyField(User, related_name='user_set')

class Meta:

database = db

So I guess my question... is it possible to do what I want using ManyToManyField? Or should I keep with the property and write my own setter?

[Charles Leifer]

For an example of how to do this, check out the example "Twitter" app. It's very similar in that a user can follow many users, and a user can have many followers.

https://github.com/coleifer/peewee/blob/master/examples/twitter/app.py#L36-L81

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