【Rails】 Scaffolding機能の使い方を初心者向けにわかりやすく解説

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rails generate scaffold モデル名 [カラム名:型]

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rails generate scaffold User name:string age:integer
#rails generate scaffold モデル名 カラム名:型 カラム名:型

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rails generate scaffold User name:string age:integer

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Rails.application.routes.draw do
  resources :users # Usersコントローラの７つのアクションにルートが設定される
end

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Prefix    Verb   URI Pattern                  Controller#Action

users     GET    /users(.:format)             users#index
          POST   /users(.:format)             users#create
new_user  GET    /users/new(.:format)         users#new
edit_user GET    /users/:id/edit(.:format)    users#edit
user      GET    /users/:id(.:format)         users#show
          PATCH  /users/:id(.:format)         users#update
          PUT    /users/:id(.:format)         users#update
          DELETE /users/:id(.:format)         users#destroy

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class UsersController < ApplicationController
  before_action :set_user, only: %i[ show edit update destroy ]

  # GET /users or /users.json
  def index
    @users = User.all
  end

  # GET /users/1 or /users/1.json
  def show
  end

  # GET /users/new
  def new
    @user = User.new
  end

  # GET /users/1/edit
  def edit
  end

  # POST /users or /users.json
  def create
    @user = User.new(user_params)

    respond_to do |format|
      if @user.save
        format.html { redirect_to @user, notice: "User was successfully created." }
        format.json { render :show, status: :created, location: @user }
      else
        format.html { render :new, status: :unprocessable_entity }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /users/1 or /users/1.json
  def update
    respond_to do |format|
      if @user.update(user_params)
        format.html { redirect_to @user, notice: "User was successfully updated." }
        format.json { render :show, status: :ok, location: @user }
      else
        format.html { render :edit, status: :unprocessable_entity }
        format.json { render json: @user.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /users/1 or /users/1.json
  def destroy
    @user.destroy
    respond_to do |format|
      format.html { redirect_to users_url, notice: "User was successfully destroyed." }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_user
      @user = User.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def user_params
      params.require(:user).permit(:name, :age)
    end
end

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class User < ApplicationRecord
end

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class CreateUsers < ActiveRecord::Migration[5.2]
  def change
    create_table :users do |t|
      t.string :name
      t.integer :age

      t.timestamps
    end
  end
end

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

<h1>Users</h1>

<table>
  <thead>
    <tr>
      <th>Name</th>
      <th>Age</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @users.each do |user| %>
      <tr>
        <td><%= user.name %></td>
        <td><%= user.age %></td>
        <td><%= link_to 'Show', user %></td>
        <td><%= link_to 'Edit', edit_user_path(user) %></td>
        <td><%= link_to 'Destroy', user, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New User', new_user_path %>

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<h1>Editing User</h1>

<%= render 'form', user: @user %><!-- _form.html.erbを呼び出す -->

<%= link_to 'Show', @user %> |
<%= link_to 'Back', users_path %>

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

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

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

  <div class="field">
    <%= form.label :age %>
    <%= form.number_field :age %>
  </div>

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

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<%# @user(特定のユーザ情報)が格納されたuserをformに渡す%>
<%= form_with(model: user, local: true) do |form| %>
    <%= form.text_field :name %><%# 他省略 %>
    <%= form.number_field :age %>
    <%= form.submit %>
<% end %>

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<form action="/users/編集するレコードのid" method="post" data-remote="true">
  <input type="hidden" name="_method" value="patch"><!--他省略-->

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<h1>New User</h1>

<%= render 'form', user: @user %><!-- _form.html.erbを呼び出す -->

<%= link_to 'Back', users_path %>

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class UsersController < ApplicationController
  def new
    @user = User.new #Userインスタンスを生成して@userへ
  end
end

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<%# @user(新しく生成されたUserインスタンス)が格納されたuserをformに渡す%>
<%= form_with(model: user, local: true) do |form| %>
    <%= form.text_field :name %><%# 他省略 %>
    <%= form.number_field :age %>
    <%= form.submit %>
<% end %>

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<form action="/users" method="post" data-remote="true">

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

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

<p>
  <strong>Age:</strong>
  <%= @user.age %>
</p>

<%= link_to 'Edit', edit_user_path(@user) %> |
<%= link_to 'Back', users_path %>

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<h1>Editing User</h1>

<%= render 'form', user: @user %><!-- _form.html.erbを呼び出す -->

<%= link_to 'Show', @user %> |
<%= link_to 'Back', users_path %>

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rails generate scaffold モデル名 [カラム名:型] オプション

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rails generate scaffold User name:string age:integer --skip-jbuilder

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rails _5.2.1_ new sample_app -d mysql # Rails5.2.1、DBはmysqlを指定

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cd sample_app # ディレクトリを移動する
rails g scaffold User name:string age:integer # scaffoldを実行
# rails g scaffold モデル名 カラム名:型 カラム名:型

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bundle exec rails db:create && bundle exec rails db:migrate