How can I use ember-concurrency with a callback function?

Question

I'd like to use ember-concurrency to handle batch validation of a collection of addresses. The address validation is done by a third party API that calls a server-side function that then 'calls back' to the client when the server has completed its work.

It seems like this would be a place to use the ember-concurrency add-on, but i can't figure out how to use it correctly. I think the challenge is that the api call to server returns immediately after the server side process is kicked off. How do i make ember-concurrency aware of the connection between the call to the server and the callback function so that the 'task' waits for the callback to be completed as a sign that the task has been completed? The way i have the code working now, 'results' is (understandably) always null.

import Component from '@glimmer/component';
import { inject as service } from '@ember/service';
import { task } from 'ember-concurrency';

export default class BatchAddressInputComponent extends Component {
    @service api;
    addressList = "";

    //addressList populated from a TextArea
    @task *DoAddressValidation ()
    {
        let results = yield this.api.BatchQueryAddresses(this.addressList);
        alert(results); //not surprisingly, 'results' is always null
    }
}
    
    
import Service from '@ember/service';

export default class ApiService extends Service {
  _api;

  //API *should* be available as a global object, imported as a <script> on
  // application start-up.
  constructor() {
    super(...arguments);
    this._api = API;
  }

  BatchQueryAddresses(addressList) {
    this._api.BatchQueryAddress(addressList, 2, this._queryAddressCallback, null, 2000);
  }

  _queryAddressCallback(result, error) {
    if (error) {
        alert("Error: " + result);
        return;
    }
    var j = JSON.stringify(result, null, ' ');
    return(j);
  }
}

Answer 1

You need to return a Promise. The new Promise(...) constructor is made for exactly this:

BatchQueryAddresses(addressList) {
  return new Promise((resolve, reject) => {
    this._api.BatchQueryAddress(
      addressList,
      2,
      (result, error) => {
        if (error) {
          reject("Error: " + result);
        } else {
          const j = JSON.stringify(result, null, ' ');
          resolve(j);
        }
      },
      null,
      2000
    );
  });
}