reactiveUtils.watch() on a custom class?

fdeters

I'm starting to lean more on `reactiveUtils.watch()` for reactivity that isn't easily handled by my JavaScript framework. Generally, things are going well, but I'm running into an issue with unit/integration tests:

A common issue is that I will want to stub or mock a JS SDK class. For example, I frequently create a fake WebMap with fake layers:

class FakeLayer {
  constructor({ id, listMode, visible, type }) {
    this.id = id;
    this.listMode = listMode;
    this.visible = visible;
    this.type = type;
  }

  when = async () => true;
}

const fakeWebMap = {
    allLayers: [
      new FakeLayer({
        id: 'layer-1',
        listMode: 'hide',
        visible: true,
      }),
      new FakeLayer({
        id: 'layer-2',
        listMode: 'hide',
        visible: false,
      }),
      new FakeLayer({
        id: 'layer-3',
        listMode: 'show',
        visible: true,
      }),
};

 

My problem is this: reactiveUtils.watch() does not seem to work on POJOs or custom classes like FakeLayer above.

In the example above, I might be testing code that watches the `visible` property on each FakeLayer and mutates `listMode` if `visible` changes. How can I implement a mock/stub testing class that works with reactiveUtils.watch()?

JoelBennett

Have you considered extending the Accessor class?  See also https://developers.arcgis.com/javascript/latest/implementing-accessor/