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

Length Validation in Rails Model

📖 Scenario: You are building a simple Rails application to manage user profiles. Each user must have a username that is not too short or too long to keep the data consistent and user-friendly.

🎯 Goal: Create a Rails model User with a username attribute. Add a length validation to ensure the username is at least 3 characters and at most 15 characters long.

📋 What You'll Learn

Create a Rails model called User with a username attribute

Add a length validation on username to require minimum 3 characters

Add a length validation on username to require maximum 15 characters

Use Rails built-in validation syntax for length

💡 Why This Matters

🌍 Real World

Length validations are common in web apps to ensure user inputs like usernames, passwords, or descriptions meet expected size limits.

💼 Career

Understanding Rails validations is essential for backend developers working with Rails to enforce data integrity and improve user experience.

1

Create the User model with username attribute

Create a Rails model called User with a string attribute username.

Ruby on Rails

# Create a Rails model User with username attribute
# Your code here

Need a hint?

Define a class User that inherits from ApplicationRecord.

2

Add minimum length configuration

Add a validation to the User model that requires the username to have a minimum length of 3 characters using validates :username, length: { minimum: 3 }.

Ruby on Rails

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

Need a hint?

Use validates :username, length: { minimum: 3 } inside the model class.

3

Add maximum length configuration

Extend the length validation on username to also require a maximum length of 15 characters using validates :username, length: { minimum: 3, maximum: 15 }.

Ruby on Rails

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

Need a hint?

Add maximum: 15 inside the length hash.

4

Complete the User model with length validation

Ensure the User model has the complete length validation on username with minimum 3 and maximum 15 characters using validates :username, length: { minimum: 3, maximum: 15 }.

Ruby on Rails

class User < ApplicationRecord
  validates :username, length: { minimum: 3, maximum: 15 }
  # Your code here if needed
end

Need a hint?

Check that the validation line is exactly as required.