so i am trying to save to a join table in a habtm relationship, but i am having problems.

from my view, i pass in a group id with:

= link_to "Create New User", new_user_url(:group => 1)

User model (user.rb)

class User < ActiveRecord::Base
has_and_belongs_to_many :user_groups
accepts_nested_attributes_for :user_groups end

UserGroups model (user_groups.rb)

class UserGroup < ActiveRecord::Base
  has_and_belongs_to_many :users
end

users_controller.rb

def new
  @user = User.new(:user_group_ids => params[:group])
end

in the new user view, i have access to the User.user_groups object, however when i submit the form, not only does it not save into my join table (user_groups_users), but the object is no longer there. all the other objects & attributes of my User object are persistent except for the user group.

i just started learning rails, so maybe i am missing something conceptually here, but i have been really struggling with this.