How can I properly interact with many-to-many relationship in Django+GraphQL?

Question

How do I properly interact with many-to-many relationship in Django+GraphQL?

I have a Game model which has a many to many relationship to User model.

class Game(models.Model):
    name = models.CharField(max_length=256, blank=True)
    users = models.ManyToManyField(to=User, blank=True, related_name='games')


class User(AbstractUser):
    email = models.EmailField(max_length=128, verbose_name='email address', blank=False)

I need to connect it to GraphQL so I can read and modify that fields via mutations.

I already have a schema to work with Game without users but now I need to add users as well

{
  games {
    edges {
      node {
        id
        name
      }
    }
  }
}

But it doesn't work when I add users because the Game table in db doesn't have a users field. It has the games_game_users table that describes their relationship.

How can I modify my code to be able to work with game.users field?

Answer 1

If you want to interact with many-to-many relationship in Django+GraphQL you should define your Nodes correctly.

That's how it should be defined for my case:

class UserNode_(DjangoObjectType):
    class Meta:
        model = User
        interfaces = (graphene.relay.Node,)


class GameNode(DjangoObjectType):
    class Meta:
        model = Game
        interfaces = (graphene.relay.Node,)

    users = graphene.List(UserNode_)

    def resolve_users(value_obj, info):
        return value_obj.users.all()

So this GraphQL request will display your games and connected users

{
  games {
    edges {
      node {
        id
        title
        users {
          id
          username
          email
        }
      }
    }
  }
}

To add or to remove users from the game use add() and remove() methods:

game.users.add(new_user)
game.users.remove(old_user)