An Enum is a data type that allows us to define a set of named constants. Rails 7.1 brings a notable enhancement to enum handling by introducing the :validate option.

It will allow more flexible and robust validation of enum values within the ActiveRecord models.

In this blog post, we’ll explore how this change affects our code and how the validations for enum values were handled in previous versions of Rails.

Before

In previous versions of Rails, if we assign an incorrect value to the enum then it used to raise an ArgumentError.

We can illustrate this by the following example.

class Holiday < ApplicationRecord

  enum type: [:national, :regional]

end

holiday = Holiday.last

holiday.type = :optional

'optional' is not a valid type (ArgumentError)

In the above snippet, we have a Holiday model with an enum type column which can take national or regional as valid holiday types.

When we tried passing optional as a holiday type it raised an ArgumentError.

After

Rails 7.1 introduced the validate option for enums. It will allow developers to enforce the validation checks before saving enum values.

Let’s try passing the validate: true to the above snippet and see the change introduced from this version.

class Holiday < ApplicationRecord

  enum type: [:national, :regional], validate: true

end

holiday = Holiday.last

holiday.type = :optional
holiday.valid? # Output: false

holiday.type = nil
holiday.valid? # Output: false

holiday.type= :national
holiday.valid? # Output: true

We can also pass additional validation options

class Holiday < ApplicationRecord

  enum type: [:national, :regional], validate: { allow_nil: true }

end

holiday = Holiday.last

holiday.type = :optional
holiday.valid? # Output: false

holiday.type = nil
holiday.valid? # Output: true

If we don’t pass the validate option it will raise the ArgumentError as in the earlier versions.

To know more about this feature, please refer to this PR