How to use offline validation in Yii2?

Question

Yii

Nowhere does it say how to use offline validation.
Let's say we created a standalone validator:

class SimpleValidator extends Validator {
    public function validateAttribute($model, $attribute) {
        $this->addError($model, $attribute, "Просто ошибка");
    }
}

How to use it now? What's next? How to specify this validator in the model so that it works?

Answer 1

['my_field', SimpleValidator::className()]