[]类未找到方法

public class Welcome extends welcomeUI {
public function Welcome() {
requestData();
}
private function requestData():void{

RequestConfig.instance.getRequestConfig(String(0), requestCallback);
}

private function requestCallback(success:Boolean):void
{

if(success)
{
loadingRes();
}

}

"TypeError: this.loadingRes is not a function\n at RequestConfig.__proto.requestCallback [as _callback]