High Performance PostgreSQL for Rails

Creating Active Record Custom Validators

As an experienced Rails developer, you’re probably familiar with Active Record validations.^[92] Active Record provides a huge list of validations, and many of them can be combined together.

This system is extensible, meaning developers can create their own validations as custom validators. Custom validators^[93] are created using object oriented design concepts we’ll explore next.

How are they set up? To create one, create a Ruby class that extends the ActiveModel::Validator class and implements a validate() instance method. The .validate method accepts a record argument. When those two ingredients are in place, you’ve created a custom validator.

Individual attributes for a model can be validated by ...