Chapter 8. Validations

I have bought this wonderful machine a computer. Now I am rather an authority on gods, so I identified the machine it seems to me to be an Old Testament god with a lot of rules and no mercy.

—Joseph Campbell

The Validations API in Active Model, along with its supplementary functionality in Active Record allows you to declaratively define valid states for your model objects. The validation methods hook into the life cycle of an Active Record model object and are able to inspect the object to determine whether certain attributes are set, have values in a given range, or pass any other logical hurdles that you specify.