Correctly Extend a Class: Constructor

Alexandre-Notos — Thu, 23 Sep 2021 21:16:07 GMT

I'm looking for guidance with how to properly extend a class with respect to its constructor. All of this is in typescript. I'm extending the Graphic class. Normally the graphics class take a GraphicProperties object. I'm my class I had new properties. I would like to change the constructor from

constructor(properties?: any) { ... }

constructor(properties?: SegmentProperties) { ... }

Also, is it possible to define the type of properties without initializing them in the constructor?

My full code is below:

import Graphic from "@arcgis/core/Graphic"; import Polyline from "@arcgis/core/geometry/Polyline"; import LineSymbol3D from "@arcgis/core/symbols/LineSymbol3D"; import LineSymbol3DLayer from "@arcgis/core/symbols/LineSymbol3DLayer"; import { subclass, property } from "@arcgis/core/core/accessorSupport/decorators"; import GraphicsLayer from "@arcgis/core/layers/GraphicsLayer"; import Point from "@arcgis/core/geometry/Point"; import * as watchUtils from "@arcgis/core/core/watchUtils"; @subclass("esri.core.Graphic.SegmentGraphic") export class SegmentGraphic extends Graphic{ @property() startPoint: Graphic; @property() endPoint: Graphic; @property({ readOnly: true }) get length(): number { return 10; } constructor(properties?: any) { super(properties); this.startPoint = properties.startPoint; this.endPoint = properties.endPoint; this.updatePolyline() this.symbol = new LineSymbol3D({ symbolLayers: [ new LineSymbol3DLayer({ size: 5, material: { color: "red" } }) ] }); this.registerWatchUtil(this.startPoint); this.registerWatchUtil(this.endPoint); } private updatePolyline() { let polyline = new Polyline({spatialReference: this.startPoint.geometry.spatialReference}); polyline.addPath([this.startPoint.geometry as Point, this.endPoint.geometry as Point]); this.geometry = polyline } private registerWatchUtil(point: Graphic){ watchUtils.when(point, "geometry", (geometry) => { this.updatePolyline() }) } }

Re: Correctly Extend a Class: Constructor

ReneRubalcava — Thu, 23 Sep 2021 21:43:53 GMT

I would probably do it like this.

class SegmentGraphic extends Graphic { // so that all props are not required constructor(params: Partial<SegmentGraphic>) {} }

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Correctly Extend a Class: Constructor

Re: Correctly Extend a Class: Constructor