Callbacks overview in Ruby on Rails - Mini Project: Build & Apply

Callbacks overview in Rails

📖 Scenario: You are building a simple Rails model to manage books in a library. You want to automatically set some values and run checks when books are created or updated.

🎯 Goal: Learn how to use Rails callbacks to run code before and after saving a record.

📋 What You'll Learn

Create a Rails model with attributes

Add a callback to set a default value before saving

Add a callback to print a message after saving

Use the correct Rails callback methods

💡 Why This Matters

🌍 Real World

Callbacks in Rails models help automate common tasks like setting default values or logging changes without repeating code.

💼 Career

Understanding callbacks is essential for Rails developers to write clean, maintainable code that reacts to data changes automatically.

1

Create the Book model with attributes

Create a Rails model class called Book that inherits from ApplicationRecord and has attributes title and status.

Ruby on Rails

class Book < ApplicationRecord
  # Your code here
end

Need a hint?

Use attr_accessor to define attributes for this example.

2

Add a before_save callback to set default status

Add a before_save callback in the Book model that sets status to 'available' if it is nil.

Ruby on Rails

class Book < ApplicationRecord
  attr_accessor :title, :status

  # Your code here
end

Need a hint?

Use before_save :set_default_status and define the method set_default_status.

3

Add an after_save callback to print a message

Add an after_save callback in the Book model that calls a method print_saved_message which prints 'Book saved successfully'.

Ruby on Rails

class Book < ApplicationRecord
  attr_accessor :title, :status

  before_save :set_default_status
  # Your code here

  private

  def set_default_status
    self.status ||= 'available'
  end
end

Need a hint?

Use after_save :print_saved_message and define the method print_saved_message with a puts statement.

4

Complete the Book model with callbacks

Ensure the Book model includes attr_accessor :title, :status, the before_save :set_default_status callback, and the after_save :print_saved_message callback with their respective methods.

Ruby on Rails

class Book < ApplicationRecord
  attr_accessor :title, :status

  before_save :set_default_status
  after_save :print_saved_message

  private

  def set_default_status
    self.status ||= 'available'
  end

  def print_saved_message
    puts 'Book saved successfully'
  end
end

# Model complete with callbacks

Need a hint?

Review all previous steps and ensure the model has all parts combined correctly.