如何在Ruby On Rails中使用联接表？

Question

I have users and books. It's a many to many relationship, so I created a join table based on questions and answers I found on this site.

 class Book < ApplicationRecord
   has_and_belongs_to_many :users
 end

 class User < ApplicationRecord
   has_and_belongs_to_many :books
 end

 class BooksUsersJoinTable < ActiveRecord::Migration[5.0]
   def change
    create_table :books_users_join_table, :id => false do |t|
        t.integer :book_id, index: false
        t.integer :user_id, index: false
    end
  end

  add_index(:books_users, [:book_id, :user_id], :unique => true)
  add_index(:books_users, :book_id)
  add_index(:books_users, :user_id)
 end

So I suppose my questions are:

1. Will this join_table work how I have it or is there a better way to have written it?

2. I just wrote the add_index lines in this file. Do I have to create indexes from the command line and if so, how do I do that?

3. How do I use this join_table in a controller?

Answer 1

This is what I use do a join

class BooksController < ApplicationController
  def index
    @books Book.all.joins(:user)
  end
end

I hope that this helps