RailsでToDoサービスを作ろう（第３回）〜ユーザを紐付ける 〜

rails generate scaffold User name:string

rails db:migrate

gem 'seed-fu', '~> 2.3'

bundle install

mkdir db/fixtures
mkdir db/fixtures/development
mkdir db/fixtures/production

User.seed do |s|
  s.id = 1 s.name = "にゅ〜ぶる"
end
User.seed do |s|
  s.id = 2 s.name = "ぶるこ"
end

rake db:seed_fu

== Seed from /Users/newburu/project/rails/todo/db/fixtures/development/user.rb
 - User {:id=>1, :name=>"にゅ〜ぶる"}
 - User {:id=>2, :name=>"ぶるこ"}

rails generate migration AddUserToTask user:references

class AddUserToTask < ActiveRecord::Migration[6.0]
  def change
    add_reference :tasks, :user, null: false, foreign_key: true
  end
end

rails db:migrate

Mysql2::Error: Cannot add or update a child row: a foreign key constraint fails (`todo_development`.`#sql-16e75_a`, CONSTRAINT `fk_rails_4d2a9e4d7e` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`))

rails db:migrate:reset

Dropped database 'todo_development'
Dropped database 'todo_test'
Created database 'todo_development'
Created database 'todo_test'
== 20200429055957 CreateTasks: migrating ======================================
-- create_table(:tasks)
   -> 0.0302s
== 20200429055957 CreateTasks: migrated (0.0303s) =============================
== 20200509005333 CreateUsers: migrating ======================================
-- create_table(:users)
   -> 0.0268s
== 20200509005333 CreateUsers: migrated (0.0268s) =============================
== 20200509043009 AddUserToTask: migrating ====================================
-- add_reference(:tasks, :user, {:null=>false, :foreign_key=>true})
   -> 0.1002s
== 20200509043009 AddUserToTask: migrated (0.1003s) ===========================

class User < ApplicationRecord
  has_many :tasks
end

class Task < ApplicationRecord
  belongs_to :user
end

rails console
※略して、「rails c」でも可

user = User.first
user.tasks.create(title: "テスト", content: "テストデータ")

task = Task.first
task.user

=> #<User id: 1, name: "にゅ〜ぶる", created_at: "2020-05-09 04:53:02", updated_at: "2020-05-09 04:53:02">

<h1>New Task</h1>

<%= render 'form', task: @task %>

<%= link_to 'Back', tasks_path %>

<%= form_with(model: task, local: true) do |form| %>
  <% if task.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(task.errors.count, "error") %> prohibited this task from being saved:</h2>

      <ul>
        <% task.errors.full_messages.each do |message| %>
          <li><%= message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

  <div class="field">
    <%= form.label :content %>
    <%= form.text_area :content %>
  </div>

  <div class="field">
    <%= form.label :deadline %>
    <%= form.date_select :deadline %>
  </div>

  <div class="actions">
    <%= form.submit %>
  </div>
<% end %>

<div class="field">
  <%= form.label :user_id %>
  <%= form.select :user_id, User.all.map { |user| [user.name, user.id] } %>
</div>

app/controllers/tasks_controller.rb
def task_params
  params.require(:task).permit(:title, :content, :deadline)
end

def task_params
  params.require(:task).permit(:title, :content, :deadline, :user_id)
end

<p id="notice"><%= notice %></p>

<p>
  <strong>Title:</strong>
  <%= @task.title %>
</p>

<p>
  <strong>Content:</strong>
  <%= @task.content %>
</p>

<p>
  <strong>Deadline:</strong>
  <%= @task.deadline %>
</p>

<%= link_to 'Edit', edit_task_path(@task) %> |
<%= link_to 'Back', tasks_path %>

<p>
  <strong>User:</strong>
  <%= @task.user %>
</p>

<p>
  <strong>User:</strong>
  <%= @task.user.name %>
</p>

class User < ApplicationRecord
  has_many :tasks, dependent: :destroy
end

# テスト用Taskを登録
user = User.first
user.tasks.create(title: "test1", content: "テスト1です")
user.tasks.create(title: "test2", content: "テスト2です")

# テスト用Taskが登録されたか確認
Task.all

# テスト用Userを削除　※ここで同時にTaskが削除される
user.destroy

# 削除されたか確認
Task.all