Session-based authentication in Ruby on Rails - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the user ID in the session after login.

Ruby on Rails

session[:user_id] = [1]

Drag options to blanks, or click blank then click option'

Aparams[:id]

Bsession[:id]

Ccurrent_user

Duser.id

Attempts:

3 left

💡 Hint

Common Mistakes

Storing the whole user object in the session instead of just the ID.

Using params[:id] which may not be the logged-in user's ID.

We store the logged-in user's ID in the session using user.id to identify the user in future requests.

2fill in blank

medium

Complete the code to find the current user from the session.

Ruby on Rails

def current_user
  @current_user ||= User.find_by(id: [1])
end

Drag options to blanks, or click blank then click option'

Asession[:user_id]

Bparams[:user_id]

Ccookies[:user_id]

Drequest.user_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using params which only holds data from the current request.

Using cookies directly without session.

The session[:user_id] holds the ID of the logged-in user, so we use it to find the user record.

3fill in blank

hard

Fix the error in the logout method to clear the session.

Ruby on Rails

def logout
  [1]
end

Drag options to blanks, or click blank then click option'

Asession.delete(:user_id)

Bsession.clear(:user_id)

Csession.remove(:user_id)

Dsession[:user_id] = nil

Attempts:

3 left

💡 Hint

Common Mistakes

Using session.clear(:user_id) which is not a valid method.

Setting session[:user_id] to nil instead of deleting it.

To log out, we remove the :user_id key from the session using session.delete(:user_id).

4fill in blank

hard

Fill both blanks to check if a user is logged in and redirect if not.

Ruby on Rails

def require_login
  unless [1]
    redirect_to [2], alert: "Please log in"
  end
end

Drag options to blanks, or click blank then click option'

Acurrent_user

Bsession[:user_id]

Clogin_path

Droot_path

Attempts:

3 left

💡 Hint

Common Mistakes

Checking session[:user_id] directly instead of current_user.

Redirecting to root_path instead of login_path.

We check if current_user exists to confirm login. If not, we redirect to the login_path with an alert.

5fill in blank

hard

Fill all three blanks to create a session-based login method.

Ruby on Rails

def login
  user = User.find_by(email: params[:email])
  if user && user.authenticate([1])
    session[[2]] = user.[3]
    redirect_to dashboard_path
  else
    flash.now[:alert] = "Invalid email or password"
    render :new
  end
end

Drag options to blanks, or click blank then click option'

Aparams[:password]

B:user_id

Cid

Dparams[:email]

Attempts:

3 left

💡 Hint

Common Mistakes

Using params[:email] instead of params[:password] for authentication.

Storing the whole user object in the session.

Using wrong session key other than :user_id.

We authenticate the user with params[:password]. Then we store the user's id in session[:user_id] to keep them logged in.

Practice

1. What does session[:user_id] typically store in a Rails application using session-based authentication?

easy

A. The user's password

B. The user's email address

C. The ID of the currently logged-in user

D. The entire user object

Solution

1. Step 1: Understand session usage in Rails

   Rails uses the session hash to store small pieces of data between requests, commonly the user ID for authentication.

2. Step 2: Identify what session[:user_id] holds

   This key stores the unique identifier of the logged-in user to recognize them on subsequent requests.

3. Final Answer:

   The ID of the currently logged-in user -> Option C

4. Quick Check:

   session[:user_id] = user ID [OK]

Hint: Remember session stores user ID, not full user data [OK]

Common Mistakes:

• Thinking session stores full user object
• Confusing user ID with password or email
• Assuming session is client-side storage

2. Which of the following is the correct way to log out a user by clearing the session in a Rails controller?

easy

A. session.clear

B. All of the above

C. session[:user_id] = nil

D. session.delete(:user_id)

Solution

1. Step 1: Review methods to clear session data

   In Rails, you can remove session data by clearing all keys, deleting a specific key, or setting a key to nil.

2. Step 2: Confirm all options effectively log out user

   All three methods remove the user ID from session, effectively logging out the user.

3. Final Answer:

   All of the above -> Option B

4. Quick Check:

   Any method removing user_id logs out user [OK]

Hint: Any method removing session[:user_id] logs out user [OK]

Common Mistakes:

• Only using session[:user_id] = nil and ignoring others
• Trying to clear session without removing user_id
• Confusing session.clear with resetting entire app

3. Given this Rails controller code snippet:

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

What happens when the user enters correct email and password?

medium

A. User ID is saved in session and redirected to dashboard

B. User is redirected to login page again

C. Session is cleared and user stays on login page

D. An error is raised because session[:user_id] is not set

Solution

1. Step 1: Analyze authentication condition

   The code checks if a user with the given email exists and if the password matches using authenticate.

2. Step 2: Understand session assignment and redirect

   If authentication passes, it stores the user's ID in session and redirects to the dashboard.

3. Final Answer:

   User ID is saved in session and redirected to dashboard -> Option A

4. Quick Check:

   Correct login sets session[:user_id] and redirects [OK]

Hint: Correct login sets session[:user_id] and redirects [OK]

Common Mistakes:

• Assuming user stays on login page after success
• Thinking session[:user_id] is not set on success
• Confusing render with redirect behavior

4. Identify the error in this logout action:

def logout
  session[:user] = nil
  redirect_to root_path
end

medium

A. No error, this code works fine

B. redirect_to should be redirect_back

C. session[:user] = nil does not clear session

D. Session key should be :user_id, not :user

Solution

1. Step 1: Check session key used for authentication

   Rails session-based authentication typically uses session[:user_id] to track logged-in user.

2. Step 2: Identify mismatch in session key

   The code sets session[:user] to nil, which does not clear the actual user ID stored in session[:user_id].

3. Final Answer:

   Session key should be :user_id, not :user -> Option D

4. Quick Check:

   Correct session key is :user_id [OK]

Hint: Use session[:user_id] to clear login, not session[:user] [OK]

Common Mistakes:

• Using wrong session key name
• Assuming setting any session key to nil logs out user
• Confusing redirect_to with redirect_back

5. You want to restrict access to a controller action so only logged-in users can see it. Which code snippet correctly checks session-based authentication before allowing access?

hard

A. before_action :require_login

def require_login
redirect_to login_path unless session[:user_id]
end

B. before_action :require_login

def require_login
redirect_to login_path if session[:user_id]
end

C. before_action :require_login

def require_login
redirect_to root_path unless session[:user_id]
end

D. before_action :require_login

def require_login
redirect_to login_path unless session[:user]
end

Solution

1. Step 1: Understand access control with before_action

   Use a method to check if session[:user_id] exists before allowing access.

2. Step 2: Identify correct redirect condition

   If session[:user_id] is missing, redirect to login page to block access.

3. Final Answer:

   Redirect to login unless session[:user_id] exists -> Option A

4. Quick Check:

   Access allowed only if session[:user_id] present [OK]

Hint: Redirect unless session[:user_id] exists to protect pages [OK]

Common Mistakes:

• Redirecting if session[:user_id] exists (wrong logic)
• Using wrong session key like :user
• Redirecting to wrong path on failure