So I have the following models set up

class User
  include Mongoid::Document
  has_and_belongs_to_many :teams, autosave: true
end

class Team
  include Mongoid::Document
  has_and_belongs_to_many :users, autosave: true
end

When I create a Team with team = Team.create users: [user] where user is a user object, everything works fine and my newly created team appears in user.teams. However, I’m getting data via POST so I only receive user ids, which leads me more or less to the following code: team = Team.create user_ids: [user.id.to_s] (production code looks of course different, user_ids are provided via params)

This also works as expected, except that the team is not stored in the user model. user.teams is still empty while team.users is saved correctly. Is this the desired behaviour?

I am using Mongoid 4 with Rails 4.