Login and logout flow in Ruby on Rails - Mini Project: Build & Apply

Login and logout flow

📖 Scenario: You are building a simple web app where users can log in and log out. This helps users access their personal dashboard securely.

🎯 Goal: Create a basic login and logout flow using Rails. You will set up user data, configure session handling, implement login logic, and add logout functionality.

📋 What You'll Learn

Create a hash called users with usernames as keys and passwords as values

Create a variable called session as an empty hash to store login state

Write a method login that takes username and password, checks credentials, and sets session[:user] if valid

Write a method logout that clears the session[:user] to log out the user

💡 Why This Matters

🌍 Real World

Login and logout flows are essential for any web app that needs user accounts and personalized access.

💼 Career

Understanding session management and authentication basics is key for backend and full-stack developers working with Rails.

1

DATA SETUP: Create user data

Create a hash called users with these exact entries: 'alice' => 'password123', 'bob' => 'secure456', and 'carol' => 'qwerty789'.

Ruby on Rails

# Create the users hash with usernames and passwords
# Your code here

Hint

Use a Ruby hash with string keys and string values for passwords.

2

CONFIGURATION: Create session hash

Create an empty hash called session to store the login state.

Ruby on Rails

users = { 'alice' => 'password123', 'bob' => 'secure456', 'carol' => 'qwerty789' }
# Create an empty session hash
# Your code here

Hint

Just create an empty hash named session.

3

CORE LOGIC: Implement login method

Write a method called login that takes username and password. Inside, check if users[username] equals password. If yes, set session[:user] = username. Otherwise, do nothing.

Ruby on Rails

users = { 'alice' => 'password123', 'bob' => 'secure456', 'carol' => 'qwerty789' }
session = {}
# Define login method
# Your code here

Hint

Use an if statement to compare the password and assign session[:user].

4

COMPLETION: Implement logout method

Write a method called logout that removes the :user key from the session hash to log out the user.

Ruby on Rails

users = { 'alice' => 'password123', 'bob' => 'secure456', 'carol' => 'qwerty789' }
session = {}

def login(username, password)
  if users[username] == password
    session[:user] = username
  end
end

# Define logout method
# Your code here

Hint

Use session.delete(:user) inside the logout method.

Practice

1. What does the session[:user_id] typically store in a Rails login flow?

easy

A. The user's email address

B. The ID of the logged-in user

C. The user's password

D. The current time of login

Solution

1. Step 1: Understand session usage in Rails login

   In Rails, session[:user_id] is used to store the unique identifier of the logged-in user to keep track of their session.

2. Step 2: Differentiate from other user data

   Passwords and emails are not stored in session for security and privacy reasons; only the user ID is stored.

3. Final Answer:

   The ID of the logged-in user -> Option B

4. Quick Check:

   session[:user_id] = user ID [OK]

Hint: Session stores user ID, not password or email [OK]

Common Mistakes:

• Thinking session stores password
• Confusing session with cookies
• Assuming session stores full user object

2. Which of the following is the correct way to clear the user session during logout in a Rails controller?

easy

A. reset_session

B. session.clear

C. session[:user_id] = nil

D. session.delete(:user_id)

Solution

1. Step 1: Identify Rails method to reset session

   The reset_session method clears the entire session safely and is the recommended way to log out a user.

2. Step 2: Compare with other options

   While session.delete(:user_id) or setting it to nil removes the user ID, reset_session is more secure as it resets the whole session.

3. Final Answer:

   reset_session -> Option A

4. Quick Check:

   Use reset_session to clear all session data [OK]

Hint: Use reset_session to fully clear session on logout [OK]

Common Mistakes:

• Only deleting user_id but leaving other session data
• Using session.clear, which doesn't regenerate the session ID
• Setting session[:user_id] to nil without resetting session

3. Given this Rails controller code for login:

def create
  user = User.find_by(email: params[:email])
  if user&.authenticate(params[:password])
    session[:user_id] = user.id
    redirect_to dashboard_path
  else
    flash[:alert] = 'Invalid login'
    render :new
  end
end

What happens if the password is incorrect?

medium

A. User is redirected to dashboard

B. User ID is saved in session

C. Application crashes with error

D. Login form is re-rendered with alert

Solution

1. Step 1: Analyze the if condition

   The condition user&.authenticate(params[:password]) returns false if password is wrong, so the else block runs.

2. Step 2: Understand else block behavior

   The else block sets a flash alert and re-renders the login form with render :new.

3. Final Answer:

   Login form is re-rendered with alert -> Option D

4. Quick Check:

   Wrong password triggers else block [OK]

Hint: Wrong password triggers else block with alert [OK]

Common Mistakes:

• Assuming redirect happens on wrong password
• Thinking session is set even if password fails
• Believing app crashes on wrong password

4. Identify the error in this logout action:

def destroy
  session[:user_id] = nil
  redirect_to login_path
end

What is the main issue with this logout method?

medium

A. It does not clear the entire session

B. It redirects to the wrong path

C. It raises a syntax error

D. It does not delete the user record

Solution

1. Step 1: Check session clearing method

   Setting session[:user_id] = nil only removes the user ID but leaves other session data intact.

2. Step 2: Understand best practice for logout

   Best practice is to use reset_session to clear all session data and prevent session fixation attacks.

3. Final Answer:

   It does not clear the entire session -> Option A

4. Quick Check:

   Partial session clearing is insecure [OK]

Hint: Partial session clearing leaves data behind; use reset_session [OK]

Common Mistakes:

• Thinking setting user_id to nil clears session fully
• Ignoring session fixation security risks
• Assuming redirect path affects logout correctness

5. You want to ensure users cannot access the dashboard without logging in. Which code snippet correctly enforces this in a Rails controller using the login session?

hard

A. before_action :require_login

def require_login
redirect_to login_path if session[:user_id].present?
end

B. before_action :require_login

def require_login
redirect_to dashboard_path if session[:user_id].nil?
end

C. before_action :require_login

def require_login
redirect_to login_path unless session[:user_id]
end

D. before_action :require_login

def require_login
redirect_to login_path if session[:user_id] == true
end

Solution

1. Step 1: Understand login check logic

   Users should be redirected to login if session[:user_id] is missing (nil or false).

2. Step 2: Analyze each option's condition

   before_action :require_login def require_login redirect_to login_path unless session[:user_id] end redirects to login unless user_id exists, correctly blocking access. Others have incorrect conditions or redirect to wrong paths.

3. Final Answer:

   before_action :require_login with redirect unless session[:user_id] -> Option C

4. Quick Check:

   Redirect to login if no user_id [OK]

Hint: Redirect unless session[:user_id] exists to block access [OK]

Common Mistakes:

• Using wrong condition logic for session check
• Redirecting to dashboard instead of login
• Checking session[:user_id] == true which is incorrect