Numeric Data with only_numeric Validation in Rails 7

The only_numeric validation, introduced in Rails 7, empowers developers to enforce stricter constraints on model attributes. This ensures that only numeric values are accepted, improving data integrity in various scenarios. Imagine collecting phone numbers or product quantities – only_numeric guarantees user input adheres to the expected format.

Using the only_numeric Validation

Here’s how to implement only_numeric validation in a Rails model:

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class Product < ApplicationRecord
  validates_numericality_of :quantity, only_numeric: true
end

This example uses the validates_numericality_of method with the only_numeric: true option. This ensures the quantity attribute contains only numbers. Any attempt to create a product with a non-numeric value in quantity will trigger validation failure, preventing the record from being saved.

Important Notes:

• Nil by Default: The numericality validation does not allow nil values by default.
• Allowing Nil: If you want to allow the attribute to be null, you can use the allow_nil: true option:

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class Product < ApplicationRecord
  validates_numericality_of :quantity, only_numeric: true, allow_nil: true
end

With this configuration, the validation will allow both numeric values and nil.

Invalid Input

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Product.create!(quantity: "10 units")
=> raises ActiveRecord::RecordInvalid with message: "Quantity is not a number"

As expected, creating a product with a string value (“10 units”) for quantity fails validation. The only_numeric option ensures the value is a number, not a combination of digits and text.

Valid Input

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Product.create!(quantity: 10)
=> #<Product id: 2, quantity: 10, created_at: ..., updated_at: ...>

Creating a product with a numeric value for quantity successfully passes validation. The record is saved and the quantity is stored as an integer in the database.