How to access 'this' in angular 2 event handler?

Question

In my Component's keydown event handler, I need to modify a propery of the component via this:

  canvasKeyHandler (event) {
    console.log('vrscene.canvasKeyHandler: event.keyCode=' + event.keyCode);
    console.log('vrscene.canvasKeyHandler: self.dolly' + this.dolly);

    CameraKeypressEvents.keyHandler(event, this.dolly) // <-- do something with this.dolly

But this.dolly is set to undefined:

vrscene.canvasKeyHandler: self.dollyundefined

vrscene.html:

<div class="container" id ="canvas-container-2">
   <canvas id="vrruntime-view"
           class="camera-keypress-events"
           tabindex="1"
           (keydown)="canvasKeyHandler($event)"
           style="border: 1px solid black;"
           >
   </canvas>
           <!--camera-keypress-events [cubeScene]="cubeScene" -->

</div>

vrscene.ts:

import {Component} from 'angular2/core';
import {Injectable} from 'angular2/core';
import WebGLRenderer = THREE.WebGLRenderer;
import {VRRenderer} from '../vrrenderer/vrrenderer'
import {CameraKeypressEvents} from '../camera-keypress-events/camera-keypress-events'

import Object3D = THREE.Object3D;
import Scene = THREE.Scene;
import PerspectiveCamera = THREE.PerspectiveCamera;
import Mesh = THREE.Mesh;
import VRControls = THREE.VRControls;
import VREffect = THREE.VREffect;

@Component ({
  selector: 'vrscene',
  templateUrl: 'app//vrscene/vrscene.html',
})

@Injectable()
export class VRScene {

  private _scene: Scene;
  camera: PerspectiveCamera;
  dolly: Object3D;
  vrControls: VRControls;
  vrEffect: VREffect;
  webVrManager;
  sphere: Mesh;
  cube: Mesh;
  BaseRotation = new THREE.Quaternion();

  constructor() {}

  //initScene(width: number, height: number, renderer: VRRenderer) {
  init(width: number, height: number, vrRenderer: VRRenderer) {
    console.log('VRScene.init: entered')
    this.scene = new THREE.Scene;

    this.camera = new THREE.PerspectiveCamera(75, width / height);
    this.camera.position.set(0, 1.5, 100);
    this.dolly = new THREE.Object3D();
    this.dolly.position.z = 50;
    this.scene.add(this.dolly);
    //
    this.dolly.add(this.camera);

    this.vrControls = new THREE.VRControls(this.camera);

    this.vrEffect = new THREE.VREffect(vrRenderer.renderer);
    this.vrEffect.setSize(width, height);
    this.webVrManager = new (<any>window).WebVRManager(vrRenderer.renderer, this.vrEffect);
    console.log('VRScene.init: this.webVrManager=' + this.webVrManager);
    this.camera.quaternion.copy(this.BaseRotation);

    var geometry = new THREE.BoxGeometry(25, 25, 25);
    var meshParms = new Object();

    meshParms['color'] = 0xff8000;

    var material = new THREE.MeshBasicMaterial(meshParms);
    //material = new THREE.MeshBasicMaterial( {color: 0xffff00, side: THREE.DoubleSide} );
    this.cube = new THREE.Mesh(geometry, material);
    this.scene.add(this.cube);

    // draw!
    vrRenderer.canvas.focus();
    //CubeOnPlaneScene.prototype.mainLoop.bind(this)
    // bind the 'this' of the canvasKeyHandler to the definition-time 'this'
    //VRScene.prototype.canvasKeyHandler.bind(this)
  }

  canvasKeyHandler (event, dolly) {
    console.log('vrscene.canvasKeyHandler: event.keyCode=' + event.keyCode);
    //console.log('vrscene.canvasKeyHandler: this.dolly' + this.dolly);
    //console.log('vrscene.

canvasKeyHandler: self.dolly' + this.dolly);
    console.log('vrscene.canvasKeyHandler: dolly' + dolly);

    //CameraKeypressEvents.keyHandler(event, this.dolly)
    //CameraKeypressEvents.keyHandler(event, VRScene.prototype.canvasKeyHandler)
    CameraKeypressEvents.keyHandler(event, dolly)
  }

  doIt() : string {
    return 'hello from VRScene'
  }

  // getters  and setters
  get scene():Scene {
     return this._scene;
  }

  set scene(scene: Scene) {
    if (scene === undefined) throw 'Please supply a scene';
    this._scene = scene;
  }

}

Key handler:

import {Directive} from 'angular2/core';
import {CubeScene} from '../cube-scene/cube-scene';
import Object3D = THREE.Object3D;
import Vector3 = THREE.Vector3;
import {Base} from '../base/base';
import Quaternion = THREE.Quaternion;


@Directive({
  selector: '[camera-keypress-events]',
  providers: [],
  //host: {},
  host: {
    '(keypress)' : 'onKeypress($event)'
  },

})

export class CameraKeypressEvents {

  constructor() {}

  static CAMERA_MOVE_DELTA = 1.2;
  static CAMERA_ROT_DELTA = 5;

  static keyHandler (event, dolly: Object3D) {
    console.log('CameraKeypressEvents.keyHandler: event.keyCode=' + event.keyCode)
    console.log('CameraKeypressEvents.keyHandler: dolly=' + dolly)   
        switch( event.keyCode) {
      case 'S'.charCodeAt(0):
        console.log('you pressed s');
        //dolly.position.z += CAMERA_MOVE_DELTA;
        dolly.translateZ(this.CAMERA_MOVE_DELTA);
        console.log('dolly.postion.x=' + dolly.position.x);
      break;

      case 'W'.charCodeAt(0):
        //console.log('you pressed s');
        //this.dolly.position.z -= this.CAMERA_MOVE_DELTA;
        dolly.translateZ(-this.CAMERA_MOVE_DELTA);
        //console.log('this.do-ly.postion.x=' + this.dolly.position.x);
      break;

      case 'A'.charCodeAt(0):
        //this.dolly.position.x -= this.CAMERA_MOVE_DELTA;
        dolly.translateX(-this.CAMERA_MOVE_DELTA);
      break;

      case 'D'.charCodeAt(0):
        //console.log('you pressed s');
        //this.dolly.position.x += this.CAMERA_MOVE_DELTA;
        dolly.translateX(this.CAMERA_MOVE_DELTA);
        //console.log('this.dolly.postion.x=' + this.dolly.position.x);
      break;

      case 'N'.charCodeAt(0):
        //this.dolly.position.y -= this.CAMERA_MOVE_DELTA;
        dolly.translateY(-this.CAMERA_MOVE_DELTA);
      break;

      case 'P'.charCodeAt(0):
        //console.log('you pressed s');
        //this.dolly.position.y += this.CAMERA_MOVE_DELTA;
        //console.log('this.dolly.postion.x=' + this.dolly.position.x);
        dolly.translateY(this.CAMERA_MOVE_DELTA);
      break;

      case 'Q'.charCodeAt(0):
        var tmpQuat = (new THREE.Quaternion()).setFromAxisAngle( new THREE.Vector3(0,1,0), Base.ONE_DEG * this.CAMERA_ROT_DELTA);
        dolly.quaternion.multiply(tmpQuat);
      break;

      case 'E'.charCodeAt(0):
        var tmpQuat = (new THREE.Quaternion()).setFromAxisAngle( new THREE.Vector3(0,1,0), Base.ONE_DEG * -this.CAMERA_ROT_DELTA);
        dolly.quaternion.multiply(tmpQuat);
      break;
    };
  }

   onKeypress (event, cubeScene) {
    console.log('CameraKeypressEvents.onKeypress: event.keyCode=' + event.keyCode)
        //event.preventDefault();
    console.log('vtClass.canvasKeyhandler: cubeScene=' + cubeScene);
    console.log(event, event.keyCode, event.keyIdentifier);

    /*
    */
  }
}

How do I either:

A) pass the instance on the keyhandler call?

I tried:

(keydown)="canvasKeyHandler($event,{{dolly}})"

B) Bind the canvasKeyHandler method to the compile time this?

I tried:

// bind the callback 'this' of the canvasKeyHandler to the definition-time 'this'
VRScene.prototype.canvasKeyHandler.bind(this)

and

  canvasKeyHandler (event) {
    ...
}.bind(this)

My apologies if this is an obvious question, but I'm just learning the Angular 2 framework and getting a little overwhelmed at this point. Do I need to do something with @Input?

Many Thanks

Answer 1

(keydown)="canvasKeyHandler($event,{{dolly}})"

should be

(keydown)="canvasKeyHandler($event,dolly)"

I don't know if this actually fixes your problem (don't really understand what the issue is)

Answer 2

The this corresponds to the instance of your component within the event handler (canvasKeyHandler). I think that using the following to configure the handler for the keydown event is enough:

(keydown)="canvasKeyHandler($event)"

I saw that you initialize the dolly property within the init method. But I can't see where this method is called. Perhaps it's the reason of your problem...