Presence validation in Ruby on Rails - Mini Project: Build & Apply

Presence Validation in Rails Model

📖 Scenario: You are building a simple Rails application to manage a list of books. Each book must have a title and an author. To ensure data quality, you want to make sure that no book can be saved without these details.

🎯 Goal: Create a Rails model Book with presence validation for the title and author attributes. This will prevent saving books without these required fields.

📋 What You'll Learn

Create a Book model with title and author attributes

Add presence validation for title and author

Use Rails validation syntax correctly

Ensure the model is ready to reject invalid records missing these fields

💡 Why This Matters

🌍 Real World

Presence validation is essential in web apps to ensure users provide required information before saving data, preventing incomplete or invalid records.

💼 Career

Understanding and implementing validations is a fundamental skill for Rails developers to maintain data integrity and build reliable applications.

1

Create the Book model with attributes

Create a Rails model called Book with string attributes title and author using attr_accessor.

Ruby on Rails

# Define the Book class with attr_accessor for title and author
# Your code here

Need a hint?

Use attr_accessor to create getter and setter methods for title and author.

2

Add ActiveModel inclusion and validation setup

Include ActiveModel::Model in the Book class to enable validations. Then, add a validation for presence of title and author using validates.

Ruby on Rails

class Book
  attr_accessor :title, :author
  # Include ActiveModel::Model and add presence validation
  # Your code here
end

Need a hint?

Use include ActiveModel::Model to add validation features. Then use validates :attribute, presence: true for each attribute.

3

Create a new Book instance with missing title

Create a new instance of Book called book with author set to 'Jane Austen' and title set to nil.

Ruby on Rails

class Book
  include ActiveModel::Model
  attr_accessor :title, :author
  validates :title, presence: true
  validates :author, presence: true
end

# Create a Book instance with author 'Jane Austen' and no title
# Your code here

Need a hint?

Use Book.new with keyword arguments to set title to nil and author to 'Jane Austen'.

4

Check if the book instance is valid

Call book.valid? to check if the book instance passes the presence validations.

Ruby on Rails

class Book
  include ActiveModel::Model
  attr_accessor :title, :author
  validates :title, presence: true
  validates :author, presence: true
end

book = Book.new(title: nil, author: 'Jane Austen')

# Check if book is valid
# Your code here

Need a hint?

Use the valid? method on the book instance to trigger validations.