Retrieve created object from InheritedResources#create

Question

In my Rails app, I have the following objects:

Group: has_many users through group_membership
GroupMembership: belongs_to user, belongs_to group
User: has_many groups through group_membership

Users can create groups. When this happens, I want to automatically add the user to the group. In my GroupsController, I have the following (extending InheritedResources):

super do |success, failure|
  if success
    GroupMembership.create(:user_id => current_user, :group_id => ???)
  ...
end

The problem is I cannot retrieve the object that super created. Is there a way to do this? Or better, is there a way to change the LockGroup model so that it always performs this association?

Answer 1

When the callback is fired, the controller already has the standard instance variable corresponding to the created group: @group !!

class GroupController < InheritedResources::Base

  def create
    super do |success, failure|
      if success
        GroupMembership.create(:user_id => current_user, :group_id => @group.id)
      ...
    end
  end

end

Answer 2

I assume the params key given for your group is :group. Then you can used the nested_attributes_for option in the model. Then you can set those in a before filter from the create action:

class User < ActiveRecord::Base
  accept_nested_attributes_for :group_membership
end

# on your controller
before_filter :add_user, :on => [:create]

def add_user
  params[:group][:group_membership_attributes] = {}
  params[:group][:group_membership_attributes][:user] = current_user
end

or you build the group membership on user initialize:

class User < ActiveRecord::Base
  def after_initialize
    build_group_membership
  end
end


# on your controller
before_filter :add_user, :on => [:create]

def add_user
  params[:group][:user] = current_user
end

and it should automagically work.