Question

I have a HABTM association between Users and Groups in my Rails 3 app. The book I’m following to learn Rails recommends running the following command line to create the join migration:

rails generate migration create_groups_users

However in the documentation it looks like I should’ve run:

rails generate migration create_groups_users_join_table

So that the following would be in my _create_groups_users.rb migration:

class CreateGroupsUsersJoinTable < ActiveRecord::Migration

Is adding join_table required?

Answer 1

Adding join_table at the end is not explicitly required. Your first command ‘create_groups_users’ is fine. I’ve done this in rails 3.0.9 and it works.

You can double check by opening up the migration file and checking that it looks like:

create_table :groups_users, :id => false do |t|
  t.integer :group_id
  t.integer :user_id
end

The :id => false is needed for a join table as it shouldn’t have its own id field.