v4.10 - extend BaseLayerView2D in typescript

01-07-2019 03:47 PM
New Contributor III


In 4.9 extending a BaseLayerView2D was simple as in the following:

import BaseLayerView2D = require("esri/views/2d/layers/BaseLayerView2D");

class ExtendedLayerView extends BaseLayerView2D {

   // implementation...


In 4.10 the typings have changed so that BaseLayerView2D is an interface instead of a class, therefore extends won't work.

Have only worked out a very hacky way to call createSubclass to make it work...but lose all static typing with the class then as well.

Any ideas how to correctly extend BaseLayerView2D using v4.10 typings? 


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2 Replies
Frequent Contributor II

This is a doc issue we can fix for 4.11. In the meantime you can work around this by copying the BaseLayerView2D typings from 4.9 into your project.

Suggested method as follows.

1. Create a typings folder with an extensions.d.ts file.

declare module "esri/views/2d/layers/BaseLayerView2D" {
  class BaseLayerView2D {
    layer: Layer;
    tiles: Tile[];
    view: MapView;
    attach(): void;
    detach(): void;
    render(renderParameters: BaseLayerView2DRenderRenderParameters): void;
    protected requestRender(): void;
    tilesChanged(added: Tile[], removed: Tile[]): void;
  export = BaseLayerView2D;

This is taken directly from the 4.9 typings.

2. Update your tsconfig.json to use the new typings file.

  "compilerOptions": {
  "include": [
    "typings/*" // this will read all .ts files in your typings folder

This should now let you use the correct typings.


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New Contributor III

Hi Rene, 

Thanks for the response!

Originally I tried the following in a custom *.d.ts file, just to create a fake export that was an object with a constructor and the right properties.

declare namespace __esriExtend {
    interface BaseLayerView2DConstructor {
        new(properties?: any): __esri.BaseLayerView2D;

    export const BaseLayerView2DBase: BaseLayerView2DConstructor;

declare module "esri/views/2d/layers/BaseLayerView2D" {
    import BaseLayerView2DBase = __esriExtend.BaseLayerView2DBase;
    export = BaseLayerView2DBase;

That produces the error - Duplicate identifier 'BaseLayerView2D'.

The same error occurs with your suggestion.

There can't be two:

               declare module "esri/views/2d/layers/BaseLayerView2D" 

in the one project.

I can get around it by commenting out the 4.10 typings module declaration, but obviously that's not ideal. Can you think of anything else sorry? If it just means waiting for 4.11, in my case that's not so bad. Is there an expected release date?



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