多対多のアソシエーションを設定する - Qiita

class CreateRoomUsers < ActiveRecord::Migration[6.0] def change create_table :room_users do |t| t.references :room, null: false, foreign_key: true t.references :user, null: false, foreign_key: true t.timestamps end end end % rails db:migrate # app/models/room.rb内 class Room < ApplicationRecord has_many :room_users has_many :users, through: :room_users end # app/models/user.rb内 class User < Applica