You have that, when a product is on development they can change its API anytime. This change is quite important though, its related on how to set the events of your form, for example, the useful beforeSubmit.
As written on the API docs: An Action Provider Widget is a widget that has declared several actions by using its 'public static function actions()'. After, a Controller can easily import all its declared actions on its 'public function actions()'.
In this tutorial i will explain how to use jui auto complete in yii2.
The Autocomplete widget enables users to quickly find and select from a pre-populated list of values as they type, leveraging searching and filtering.