Rails Tutorial Chapter 8 Notes

It is a memorandum of Chapter 8.


Rails 6.0.3 Ruby 2.6.3

table of contents

1 session and cookies 2 Flash message display 3 Flow of creating and using helper method 4 How to install jquery and bootstrap 5 Do not log in again after signing up

1 session and cookies

** HTTP **, which is used for daily communication, is a ** stateless protocol **. What is stateless? Please display the page of XX on the browser side (request) → The page of XX is on the server side! The exchange of (response) is called a transaction, but once the exchange is completed, it is completely forgotten.

In other words, if you log in on the member site and then send a request to visit the purchase page for this product, you've forgotten your previous login interaction, so ** Who are you? It becomes **.

To prevent this, the session is set to hold the user's ID.

And it is ** cookies ** that are used to implement that session. Cookies are small, kist data that can be stored in your browser. The login function is created by storing the user's ID when logging in here and deleting the one stored in cookies when logging out.

2 Flash message display

The flash message implemented in Chapter 7 that is displayed at the time of new registration was associated with the ActiveRecord object, but since ActiveRecord is not used at the time of the session, it needs to be created by another method.


class SessionsController < ApplicationController
  def new

  def create
    user = User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      #Redirect to user information page after user login
      flash.now[:danger] = 'Invalid email/password combination'
      render 'new'

As an implementation flow, Use the flash method when you want to display it. Since it is laid out including CSS in application.html.erb, it is automatically displayed in this one line.

Also, since the flash method alone causes a small bug that does not disappear even if it is re-rendered, use the flash.now method that includes the function to turn off the display when a request occurs after displaying the flash message.

3 Flow of creating and using helper methods

At this point, conditional branching occurs frequently depending on whether or not you are logged in for each Controller. If you concisely summarize the code each time as a method, the code will be simplified, so the flow of creating and using the method yourself will be summarized.

  1. Load the helper module into application_controller.rb (this time sessions_helper.rb)


class ApplicationController < ActionController::Base
  include SessionsHelper
  1. Create your own method in the helper file (this time log_in method)


module SessionHelper
  def log_in(user)
    session[:user_id] = user.id
  1. Used in Controller file


  def create
  log_in user

By doing this, you can actually use the method. This time, the content of the log_in method is also one line, but if you assume that you will create a method with multiple lines in the future and repeat the same operation, by doing this, you can improve readability by setting the method name. It leads to being DRY.

4 How to install jquery and bootstrap

Has the setting method changed from Rails6? It seems that it may be, so this time I will summarize the setting method in Rails 6.

  1. Install with yarn
$ yarn add [email protected] [email protected]
  1. Add jQuery settings to Webpack


const { environment } = require('@rails/webpacker')

const webpack = require('webpack')
  new webpack.ProvidePlugin({
    $: 'jquery/src/jquery',
    jQuery: 'jquery/src/jquery'

module.exports = environment
  1. Requires / import required JS files


import "bootstrap"

5 Do not log in again after signing up

Is it easy to forget if you create a login function after creating a signup function? However, when I actually sign up, I am not logged in.

The actual movement is that the ** show ** view of / users/◯ is displayed with redirect_to @user, but since the user ID is not saved in the session, the created using the session The current_userandlogged_in` methods cannot be used, or false is returned.

To prevent this from happening, don't forget log_in @ user when the user is saved with the create action during signup.

It may not be the time to write it, but if you find yourself annoyed with user registration, if you have to re-enter it on the login screen after new registration, gently close the app. I think. .. Lol

A memo for a little usability.

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