Rails 4 habtm migration

Kick-Off: First Rails 4 Application with HABTM Association

Puneet PandeyLeave a comment

Hello Folks,

Its been a long time since I’ve not written a post. Now, I realize that it’s time to share some useful snippet with all of you.

Recently, I got a chance to get my hands cleaned with Rails 4. So much is happening around Rails community and with the rapid development of Rails 4, I was finding it bit difficult to keep my momentum going.

Well, leave all this apart. Now, by putting some extra efforts my system is ready with:

Ruby 2.1 & Rails 4.1

In order to start with my first Rails 4 Application, I took HABTM Association (weird, isn’t it?). It came randomly into my mind. However, I will dig into other associations as well with time, but to start with let’s take HABTM association with example.

I assume most of you are aware what changes Rails 4 has introduced. If you’re new to Rails 4 or would like to re-visit the changes, here’s the most useful link I’ve found. Just take a look.

Once you’re sure about changeset in Rails4, let’s draw an example:

Prerequisites:

  • Ruby 1.9.2+
  • Rails 4.1.0+
  • Traditional Database (MySQL/Postgres)

Key-Entities:

  • Person Model
  • Communtiy Model
  • A Join Table

Defining the Relationships & creating tables:


#{PATH_TO_APP}$ rails g model Person name:string email:string
#{PATH_TO_APP}$ rails g model Community name:string description:text
class Person < ActiveRecord::Base
has_and_belongs_to_many :communities
end
class Community < ActiveRecord::Base
has_and_belongs_to_many :persons
end
class CreatePeople < ActiveRecord::Migration
def change
create_table :people do |t|
t.string :name, null: false
t.string :email, null: false
t.timestamps
end
end
end
class CreateCommunities < ActiveRecord::Migration
def change
create_table :communities do |t|
t.string :name, null: false
t.text :description
t.timestamps
end
end
end
# {PATH_TO_APP}$ rails g migration CreateJoinTablePersonCommunity person community
# invoke active_record
# create db/migrate/20140708122358_create_join_table_person_community.rb
class CreateJoinTablePersonCommunity < ActiveRecord::Migration
def change
create_join_table :people, :communities, column_options: {null: true} do |t|
# t.index [:person_id, :community_id]
# t.index [:community_id, :person_id]
end
end
end

view raw

my-habtm.rb

hosted with ❤ by GitHub

For rest of the code-flow (controllers, views) you can download the zip of the application from my GitHub page, run it on your local and see Rails4 HABTM in action.

Happy Coding 🙂