Hi,

See https://github.com/mongoid/mongoid/issues/1838 for a description of my setup. But using Mongoid 2.4.6 I get errors with the following:

class Game
  include Mongoid::Document
  has_and_belongs_to_many :users, inverse_of: nil
end

class User
  include Mongoid::Document
end

g = Game.first
u = User.first

g.users << u
g.save!

Mongoid::Errors::Validations: Validation failed - Users is invalid.
from /Users/joel/.rvm/gems/ruby-1.9.2-p180@joel/bundler/gems/mongoid-08170f553f1c/lib/mongoid/persistence.rb:254:in `fail_validate!'
from /Users/joel/.rvm/gems/ruby-1.9.2-p180@joel/bundler/gems/mongoid-08170f553f1c/lib/mongoid/persistence.rb:76:in `save!'
from (irb):12
from /Users/joel/.rvm/gems/ruby-1.9.2-p180@joel/gems/railties-3.2.2/lib/rails/commands/console.rb:47:in `start'
from /Users/joel/.rvm/gems/ruby-1.9.2-p180@joel/gems/railties-3.2.2/lib/rails/commands/console.rb:8:in `start'
from /Users/joel/.rvm/gems/ruby-1.9.2-p180@joel/gems/railties-3.2.2/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'

This also happens if I use g.users.push etc.

The only way I can get this to work is

g.user_ids << u.id

but that seems to break the abstraction of relations ...

Any ideas?

Thanks!