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

Format Validation in Rails Models

📖 Scenario: You are building a simple Rails application to store user profiles. Each user must have a username that only contains letters and numbers, and an email address that follows a standard email format.

🎯 Goal: Create a Rails model called User with attributes username and email. Add format validations to ensure the username contains only letters and numbers, and the email is in a valid email format.

📋 What You'll Learn

Create a User model with username and email attributes

Add a format validation for username to allow only letters and numbers

Add a format validation for email to ensure it matches a standard email pattern

Use Rails built-in validation helpers and regular expressions

💡 Why This Matters

🌍 Real World

Format validations are essential in web apps to ensure user input meets expected patterns, preventing errors and improving data quality.

💼 Career

Understanding how to apply format validations in Rails models is a common task for backend developers working on user authentication and data integrity.

1

Create the User model with username and email attributes

Create a Rails model called User with string attributes username and email.

Ruby on Rails

# Create User model with username and email attributes
# Your code here

Need a hint?

Use rails generate model User username:string email:string to create the model and attributes.

2

Add a format validation for username

Add a format validation to the User model that ensures username contains only letters and numbers using the regular expression /\A[a-zA-Z0-9]+\z/.

Ruby on Rails

class User < ApplicationRecord
  # Add format validation for username here
  # Your code here
end

Need a hint?

Use validates :username, format: { with: /\A[a-zA-Z0-9]+\z/ } to restrict characters.

3

Add a format validation for email

Add a format validation to the User model that ensures email matches the regular expression /\A[^@\s]+@[^@\s]+\.[^@\s]+\z/ to validate standard email format.

Ruby on Rails

class User < ApplicationRecord
  validates :username, format: { with: /\A[a-zA-Z0-9]+\z/, message: "only allows letters and numbers" }
  # Add format validation for email here
  # Your code here
end

Need a hint?

Use validates :email, format: { with: /\A[^@\s]+@[^@\s]+\.[^@\s]+\z/ } to check email format.

4

Complete the User model with both validations

Ensure the User model includes both format validations for username and email as specified.

Ruby on Rails

class User < ApplicationRecord
  validates :username, format: { with: /\A[a-zA-Z0-9]+\z/, message: "only allows letters and numbers" }
  validates :email, format: { with: /\A[^@\s]+@[^@\s]+\.[^@\s]+\z/, message: "must be a valid email address" }
  # Model complete
end

Need a hint?

Check that both validations are present in the model.