Join tables in Rails

Let’s say you have a users table and a shows table. A user has_many shows and a show can have_many users. You’d need to set up a join table for this.

In our example, we’ll first generate a join table migration by running rails generate migration add_users_shows_join_table in the terminal.

class AddUsersShowsJoinTable < ActiveRecord::Migration[7.0]  
  def change  
      create_table :users_shows do |t|  
          t.references :user  
          t.references :show  
      end
  end  
end

I’d rather use a has_many :through association. I’m going to create a model for the users_shows table. The tricky part is that the model has to be singular. The table is users_shows but the model has to be called users_show.rb.

# users_show.rb
class UsersShow < ApplicationRecord  
  belongs_to :user  
  belongs_to :show  
end

# user.rb
class User < ApplicationRecord  
  has_many :users_shows  
  has_many :shows, through: :users_shows  
end

# show.rb
class Show < ApplicationRecord  
  has_many :users_shows  
  has_many :users, through: :users_shows  
end

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