[Ruby on Rails] How to use session method


I'm kosuke, a rails beginner. I'm learning rails and the usage of session may be unclear, so I will summarize it as a memorandum.

What is a session?

The session is mainly used for the login function and can keep the login status. By holding a session, you can be treated as a registered user until you log out once you log in. (If you close the browser, it disappears.)

Without session functionality, you would have to keep logging in every time you navigate the page.

In order to implement the session, it is necessary to inform the browser of each user.

How to define

Define a method to grant a session somewhere. In the code below, the user id is given a session named " user_id ".

This will automatically create and save the encrypted user id in the user's browser. By saving the user id on the browser, the user information can be retained.


#Method to grant session
  def log_in(user)
    session[:user_id] = user.id

The code below is the action when implementing login. If the user's password authentication is correct, I try to give the user a session.


def create
    user = User.find_by(email: params[:session][:email].downcase)
    if user && user.authenticate(params[:session][:password])
      redirect_to user
      flash.now[:danger] = 'Invalid email/password combination'
      render 'new'

How to delete a session

You can delete the session by changing the value of the given session [: user_id] to nil or deleting it.

#Set the value to "nil"
session[:user_id] = nil


#Delete the value

How to define current_user

You can use session to return the currently logged in user (if any).


#Represents the currently logged in user.
def current_user
  if session[:user_id] #user_If you have a session called id, set it to "true"
    User.find_by(id: session[:user_id])

How to use the current_user method


#Show the name of the currently logged in user
<%= current_user.name %>


#Display a link to the name and user information of the currently logged in user.
<%= link_to current_user.name, user_path(current_user) %>


rails tutorial Chapter 8 Login, logout https://railstutorial.jp/chapters/log_in_log_out?version=4.2

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