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

Numericality Validation in Rails Model

📖 Scenario: You are building a simple Rails application to manage products. Each product has a price that must be a number. To keep data clean, you want to ensure that the price is always a number when saving a product.

🎯 Goal: Learn how to add numericality validation to a Rails model attribute to ensure only numbers are accepted.

📋 What You'll Learn

Create a Rails model called Product with an attribute price

Add a numericality validation to the price attribute

Allow only numeric values for price

Ensure the validation is active when saving a product

💡 Why This Matters

🌍 Real World

Validations like numericality ensure that data entered into your app is correct and prevents errors later on.

💼 Career

Rails developers often add validations to models to enforce business rules and data integrity.

1

Create the Product model with a price attribute

Create a Rails model called Product with an attribute price of type decimal.

Ruby on Rails

# Create the Product model with a price attribute
# Your code here

Need a hint?

Use rails generate model Product price:decimal to create the model and migration.

2

Add a numericality validation configuration

Inside the Product model, add a validation line that sets up numericality validation for the price attribute.

Ruby on Rails

class Product < ApplicationRecord
  # Add numericality validation for price
  # Your code here
end

Need a hint?

Use validates :price, numericality: true inside the model class.

3

Test the numericality validation in the model

Write a method inside the Product model called valid_price? that returns true if the product is valid and false otherwise, using the built-in valid? method.

Ruby on Rails

class Product < ApplicationRecord
  validates :price, numericality: true

  # Define valid_price? method
  # Your code here
end

Need a hint?

Use def valid_price? and inside it call valid? to check validations.

4

Complete the model with validation and method

Ensure the Product model includes the price attribute, the numericality validation, and the valid_price? method as defined.

Ruby on Rails

class Product < ApplicationRecord
  validates :price, numericality: true

  def valid_price?
    valid?
  end
end

# Model complete

Need a hint?

Make sure all parts are present: class, validation, and method.