Implementation of Ruby on Rails login function (Session)


Implement login function using session. Understand how to use session (session [: user_id] = 1)

What is a session

A mechanism for realizing stateful communication.

In normal browser (stateless) communication, every time a page changes, all the information on the previous page is destroyed. In other words, even if you log in on the previous page, the information that you are logged in is not inherited when you move to the next page, so you will be required to log in every time you move. (Very inconvenient)

Therefore, it is necessary to realize stateful communication that can take over the information on the previous page. Specifically, stateful communication can be realized by storing data in a cookie.

This goal and my environment

Create a login function without using gem "devise"

Ruby 2.6.3 Rails Use gem "bcrypt" (for password encryption)


Create sign in (new registration) function


#File creation ~ rails s
mkdir rails
cd rails

rails new rails_login_session
cd rails_login_session

rails s

Create a file to add login function localhost: 3000 and say Yay! You ’re on Rails!

Gemfile and terminal

gem "bcrypt"

bundle install

Start an editor (Atom, VScode, etc.), uncomment the gem "bcrypt" in the Gemfile, and bundle install in the terminal


rails g model User email:uniq password:digest

#Make sure the file is generated
rails db:migrate

Creating a User model


rails g controller home top
rails g controller users new show 


Rails.application.routes.draw do
  root 'home#top'
  resource :user, only: [:new, :create, :show]

Creating a home controller and users controller Routing changes


<h1>sign up</h1>

<%= form_with model: @user, url: user_path, local: true do |f| %>
    <div class="field">
        <%= f.label :email %>
        <%= f.text_field :email %>

    <div class="field">
        <%= f.label :password %>
        <%= f.password_field :password %>

    <div class="field">
        <%= f.label :password_confirmation %>
        <%= f.password_field :password_confirmation %>

        <%= f.submit "sign up" %>
<% end %>


class UsersController < ApplicationController
  def new
    @user =

  def create
    user =
      session[:user_id] =
      redirect_to user_path, notice: "you have successfully sign in"
      render :new

  def show

  def user_params
    params.require(:user).permit(:email, :password, :password_confirmation)

After starting the server with rails s, access localhost: 3000 / user / new and try signing in with an appropriate email address and password. OK if you can confirm that there are no errors

Creating a login function


rails g controller sessions new

Create sessions controller


root 'home#top'
resource :user, only: [:new, :create, :show]
#Add the following 3 lines
get 'login', to: "sessions#new"
post 'login', to: "sessions#create"
delete 'logout', to: "sessions#destroy"

Routing changes


lass SessionsController < ApplicationController
  def new

  def create
    user = User.find_by_email(params[:email])
    if user && user.authenticate(params[:password])
      session[:user_id] =
      redirect_to user_path, notice: "you have successfully login"
    else[:alert] = "Email or Password is invalid"
      render :new

create create action



<%= form_with url: login_path, local: true do |f| %>
    <div class="field">
        <%= f.label :email %><br>
        <%= f.text_field :email %>

    <div class="field">
        <%= f.label :password %><br>
        <%= f.password_field :password %>

        <%= f.submit "Login" %>
    <%= link_to "Sign up", new_user_path %>
<% end %>

Create view I also added <% = link_to "Login", login_path%> to the line under submit in users / new.html.erb. After confirming that you can log in successfully, display a flash message next.


#Add the following two lines and enclose yield in div tag
    <%= notice %>
    <%= alert %>
    <div class="container">
      <%= yield %>

Now you will see the flash message. I plan to apply css to div class = "conteiner" later, so add a div tag.

Creating a logout function


def destroy
  session[:user_id] = nil
  redirect_to root_path, notice: "you have successfully logout"

Added destroy action



<p>you are login</p>
<%= link_to "Logout", logout_path, method: :delete %>

If you have a logout button, you can create a view appropriately Check if you can log out with rails s and see a flash message.

Other adjustments



<%= link_to "Sign up", new_user_path %>
<%= link_to "Log in", login_path %>

You can now log in and register from the top page.


class ApplicationController < ActionController::Base
    helper_mathod :current_user

    def login?
        if current_user.nil?
            redirect_to login_path, alert: "you have to login"

    def already_login?
        unless current_user.nil?
            redirect_to user_path, notice: "you are already login"

    def current_user
        if session[:user_id]
            current_user ||= User.find(session[:user_id])


#Add above new action
before_action :already_login?, except: :destroy


#Add above new action
before_action :already_login?, only: [:new, :create]
before_action :login?, only: :show

It is problematic for a logged-in user to go to the login screen or the new registration screen. On the contrary, there is a problem that a user who is not logged in can enter the user screen. This solved the above two problems.



<p>you are login as "<strong><%= %></strong>"</p>
<%= link_to "Logout", logout_path, method: :delete %>

Changed to be able to display the email address of the user logged in to users / show.html.erb


   text-align: center;

   margin: 20px 0 20px;

   width: 400px;
   padding: 10px 15px;
   font-size: 16px;
   border-radius: 3px;
   border: 2px solid #ddd;

that's all.

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