TypeScript - retain scope in event listener - scope

Question

I am converting my AS3 codebase to TypeScript and run into this error:
AS3 code:
private function loadDataXml(assetsXml : String) : void {
var loader : URLLoader = new URLLoader();
loader.addEventListener(Event.COMPLETE, handleDataLoaded);
loader.load(new URLRequest(assetsXml));
}
private function handleDataLoaded(event : Event) : void {
var xml_data : XML = new XML(event.target.data);
parseData(xml_data);
.........
}
private function parseData(xml_data : XML) : void {
......
}
TypeScript code
private loadDataXml(assetsXml : string) {
var xmlRequest:XMLHttpRequest = new XMLHttpRequest();
xmlRequest.addEventListener("load",this.handleDataLoaded, false);
xmlRequest.open("GET", assetsXml, false);
xmlRequest.setRequestHeader("Content-Type", "text/xml");
xmlRequest.send(null);
}
private handleDataLoaded(evt:Event) {
var xmlDoc:Document = (<XMLHttpRequest> evt.target).responseXML;
this.parseXMLData(xmlDoc);
......
}
private parseData(xmlDoc:Document):void {
......
}
and I get this error "Uncaught TypeError: Object # has no method 'parseData'" because of this line xmlRequest.addEventListener.....
I have tried using arrow function but still couldn't fix it (and i don't think I use it correctly)

Answer 1

When you need to pass functions around use the new lambda syntax for member variables (introduced in TypeScript 0.9.1):
private loadDataXml(assetsXml : string) {
var xmlRequest:XMLHttpRequest = new XMLHttpRequest();
// you are passing a member function Use lambda to define this function:
xmlRequest.addEventListener("load",this.handleDataLoaded, false);
xmlRequest.open("GET", assetsXml, false);
xmlRequest.setRequestHeader("Content-Type", "text/xml");
xmlRequest.send(null);
}
private handleDataLoaded = (evt:Event) => { // Since you want to pass this around
var xmlDoc:Document = (<XMLHttpRequest> evt.target).responseXML;
this.parseXMLData(xmlDoc); // you will get the correct this here
......
}
private parseData(xmlDoc:Document):void {
......
}

Answer 2

Try binding to the scope
xmlRequest.addEventListener("load",this.handleDataLoaded.bind(this), false);