src/Base/Widget.php
public function init()
    {
        parent::init();
        $this->checkAppPersistence();
        $this->emit(self::EVENT_INIT, [$this]);
    }
public function init()
    {
        parent::init();
        $this->checkAppPersistence();
        $this->emit(self::EVENT_INIT, [$this]);
    }
Initializes the object.
This method is called at the end of the constructor.
The default implementation will trigger an [[EVENT_INIT]] event.