topic Re: Set Property of a Class with Return Value From async Request in ArcGIS JavaScript Maps SDK Questions

Set Property of a Class with Return Value From async Request

BenRomlein — Wed, 11 Mar 2020 15:19:24 GMT

Using JS API 4.14, I have a custom Accessor class serving as the view model to a UI widget. I want to query a server to get a list of service groups available, and render that list in the UI. I have a property in my class that I want to set to the return value of the request:

@property()
layerGroups: string = null;

I'm trying to use the code below to make the request and set the value, but this does not work. No console error, but the value of layerGroups remains null. I assume because request is an async operation, so it doesn't have access to the return value at the right time.

> widget.viewModel.layerGroups
> null

const getLayerGroups = request("https://my.server/arcgis/rest/", {query: {f: "json"}, responseType: "json"}).then(response => this.set(this.layerGroups, response.data.folders));

Normally, I'd just nest the rest of my code in the callback and I'd have easy access to the returned value. But the Accessor class/widget code is more compartmentalized, and I'm not sure how and where to implement things.

How can I make this work? Do I need to put my async operations in a different lifecycle section of my class (I've only tried them in the constructor)? Is this a scoping issue? Appreciate any advice you have. Thanks!

EDIT: request here is the esri/request:

import request = require("esri/request");

Re: Set Property of a Class with Return Value From async Request

BenRomlein — Mon, 23 Mar 2020 12:34:13 GMT

bump...

Still looking for advice on this is anyone has employed a similar work-flow.

Re: Set Property of a Class with Return Value From async Request

BenRomlein — Wed, 08 Apr 2020 14:27:49 GMT

bump.
Anyone have anything on this?

Re: Set Property of a Class with Return Value From async Request

BenRomlein — Fri, 24 Jul 2020 14:26:43 GMT

In case anyone needs this, here's how I got it to work:

private async _getLayerGroups() {

let layerGroups = await request("https://gis.server.com/arcgis/rest/", {query: {f: "json"}, responseType: "json"}).then(response => response.data.folders);

You need to nest the request call in an async function and use await to make sure the value is available. This code returns an array, so I had to change the property type accordingly also.