Session handling in Ruby on Rails - Mini Project: Build & Apply

Session Handling in Rails

📖 Scenario: You are building a simple login system for a website using Ruby on Rails. You want to remember which user is logged in by using sessions.

🎯 Goal: Build a basic session handling system in Rails that stores a user's ID in the session when they log in and clears it when they log out.

📋 What You'll Learn

Create a controller with a login action that sets the session user ID

Create a variable to hold a fixed user ID for login simulation

Use session hash to store and clear the user ID

Add a logout action that clears the session user ID

💡 Why This Matters

🌍 Real World

Session handling is essential for user login systems on websites to remember who is logged in.

💼 Career

Understanding session management is a key skill for web developers working with Rails or any web framework.

1

Create a SessionsController with a login action

Create a controller called SessionsController with a method login that sets a session key :user_id to 1.

Ruby on Rails

# Create SessionsController with login method
class SessionsController < ApplicationController
  # Your code here
end

Hint

Use session[:user_id] = 1 inside the login method to store the user ID.

2

Add a fixed user ID variable for login simulation

Inside the SessionsController, create a private method called fixed_user_id that returns 1. Then update the login method to set session[:user_id] to the value returned by fixed_user_id.

Ruby on Rails

class SessionsController < ApplicationController
  def login
    # Your code here
  end

  # Your code here
end

Hint

Define a private method fixed_user_id that returns 1. Use it in login to set the session.

3

Add a logout action to clear the session user ID

Add a method logout in SessionsController that removes the :user_id key from the session by setting session[:user_id] = nil.

Ruby on Rails

class SessionsController < ApplicationController
  def login
    session[:user_id] = fixed_user_id
  end

  def logout
    # Your code here
  end

  private

  def fixed_user_id
    1
  end
end

Hint

Set session[:user_id] = nil inside the logout method to clear the session.

4

Add routes for login and logout actions

In the config/routes.rb file, add routes for login and logout actions in SessionsController using get method. Use get '/login', to: 'sessions#login' and get '/logout', to: 'sessions#logout'.

Ruby on Rails

# Add routes for login and logout
# Your code here

Hint

Use get '/login', to: 'sessions#login' and get '/logout', to: 'sessions#logout' in routes.rb.

Practice

1. What is the main purpose of using session in a Rails application?

easy

A. To style the webpage dynamically

B. To handle file uploads

C. To connect to the database

D. To store user data across multiple requests

Solution

1. Step 1: Understand what sessions do

   Sessions keep data between different pages or requests for the same user.

2. Step 2: Identify the correct purpose

   Storing user data like login status or preferences is the main use of sessions.

3. Final Answer:

   To store user data across multiple requests -> Option D

4. Quick Check:

   Sessions remember user info across pages = B [OK]

Hint: Sessions keep user info between pages [OK]

Common Mistakes:

• Confusing sessions with styling or database connections
• Thinking sessions handle file uploads

2. Which of the following is the correct way to store a user's name in the session in Rails?

easy

A. session = { name: 'Alice' }

B. session[:name] = 'Alice'

C. session.name = 'Alice'

D. session('name') = 'Alice'

Solution

1. Step 1: Recall session syntax in Rails

   Sessions use a hash-like syntax with square brackets and symbols for keys.

2. Step 2: Match the correct syntax

   Assigning with session[:name] = 'Alice' is the proper way.

3. Final Answer:

   session[:name] = 'Alice' -> Option B

4. Quick Check:

   Use session[:key] = value syntax = A [OK]

Hint: Use session[:key] = value to store data [OK]

Common Mistakes:

• Using assignment with equals on session itself
• Trying to call session like a method
• Using dot notation which is invalid

3. What will be the output of the following Rails controller code snippet?

session[:count] ||= 0
session[:count] += 1
render plain: session[:count]

medium

A. nil

B. 0

C. 1

D. Error

Solution

1. Step 1: Understand the ||= operator

   If session[:count] is nil or false, it sets it to 0; otherwise, it keeps the value.

2. Step 2: Increment the count

   After setting to 0 if needed, it adds 1, so the value becomes 1.

3. Final Answer:

   1 -> Option C

4. Quick Check:

   Initialize or keep count, then add 1 = 1 [OK]

Hint: ||= sets default, then += increments [OK]

Common Mistakes:

• Thinking ||= 0 sets count to 0 every time
• Expecting output 0 instead of 1
• Assuming session[:count] is nil after increment

4. Identify the error in this Rails controller code that tries to clear the session:

def logout
  session.clear()
  redirect_to root_path
end

medium

A. No error; code correctly clears the session

B. Missing parentheses in session.clear call

C. session.clear should be session.delete_all

D. session.clear is not a valid method

Solution

1. Step 1: Check session clearing methods in Rails

   Rails session supports clear method to remove all keys.

2. Step 2: Verify syntax and usage

   Calling session.clear() is valid and clears the session.

3. Final Answer:

   No error; code correctly clears the session -> Option A

4. Quick Check:

   session.clear() clears session correctly = D [OK]

Hint: session.clear() empties session data correctly [OK]

Common Mistakes:

• Thinking session.clear() is invalid
• Confusing with database delete methods
• Assuming parentheses are mandatory or cause error

5. You want to store a user's preferred language in the session only if it is not already set. Which code snippet correctly does this in a Rails controller?

hard

A. All of the above

B. session[:language] ||= params[:language]

C. session[:language] = params[:language] if session[:language].nil?

D. session[:language] = params[:language] unless session[:language]

Solution

1. Step 1: Understand the goal

   We want to set session[:language] only if it is not already set.

2. Step 2: Analyze each option

   session[:language] = params[:language] if session[:language].nil? uses if session[:language].nil?, which sets only if nil.
   session[:language] ||= params[:language] uses ||= which sets if false or nil.
   session[:language] = params[:language] unless session[:language] uses unless session[:language], which sets if false or nil.
   All three effectively do the same thing.

3. Final Answer:

   All of the above -> Option A

4. Quick Check:

   All three set only if session[:language] is unset = C [OK]

Hint: ||= or conditional assignment both work [OK]

Common Mistakes:

• Thinking only ||= works
• Confusing unless with if
• Setting session unconditionally