yii\rest\ActiveController::init PHP Method

    public function init()
    {
        parent::init();
        if ($this->modelClass === null) {
            throw new InvalidConfigException('The "modelClass" property must be set.');
        }
    }

 public function init()
 {
     if (!$this->modelName) {
         $this->modelName = StringHelper::basename(get_class($this), 'Controller');
     }
     if (!$this->modelClass) {
         $modelClass = 'app\\models\\' . $this->modelName;
         if (class_exists($modelClass)) {
             $this->modelClass = $modelClass;
         } else {
             $modelClass = 'app\\models\\readonly\\' . $this->modelName;
             if (class_exists($modelClass)) {
                 $this->modelClass = $modelClass;
             }
         }
     }
     if (!$this->filterModelClass) {
         $filterModelClass = 'app\\models\\search\\' . $this->modelName . 'Search';
         if (class_exists($filterModelClass)) {
             $this->filterModelClass = $filterModelClass;
         } else {
             $filterModelClass = 'app\\models\\readonly\\search\\' . $this->modelName . 'Search';
             if (class_exists($filterModelClass)) {
                 $this->filterModelClass = $filterModelClass;
             }
         }
     }
     parent::init();
 }