Async actions, 1 way binding + runloop

components.my-component.js

import Ember from 'ember';
import { run } from '@ember/runloop';

export default Ember.Component.extend({
  didInsertElement(){
    this.set('currentIndex', 0);
    this.set('currentNumber', this.numbers[this.currentIndex]);  
  },
  actions: {
    showNext(){
      let index = this.currentIndex;
      if(index === this.numbers.length - 1){
        this.fetchNext().then((nextSet) => {
          this.set('currentIndex', 0);
          this.set('callbackNumbers', this.numbers.slice(0));
          run.next(this, () => {
             this.set('syncNumbers', this.numbers.slice(0));
          });
          this.set('currentNumber', this.numbers[this.currentIndex]);
        });
      }else{
          this.set('currentIndex', this.currentIndex + 1);
          this.set('currentNumber', this.numbers[this.currentIndex]);
    	}
  	}
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  init(){
    this.set('numbers', ["one","two","three"]);  
  },
  appName: 'Ember Twiddle',
  actions: {
    fetchNext(){
      return Ember.RSVP.resolve(["four", "five", "six"]).then((result) => {
        this.set('numbers', result);
        return result;
      });
    }
  }
});

templates.application.hbs

<p>In the following component, I have collection of numbers and a current index. With each press of the next button, I bump the index until I reach end of the page, at which point I fetch the next list and set the index back to zero.</p>
{{my-component numbers=numbers fetchNext=(action 'fetchNext')}}

templates.components.my-component.hbs

{{currentNumber}}
<br>
<button {{action 'showNext'}}>Next</button> 

<h5>Current Index</h5>
<p>{{currentIndex}}</p>

<h5>Current list</h5>
<ul>
{{#each numbers as |num|}}
  <li>{{num}}</li>
{{/each}}
</ul>

<h5>List in callback</h5>
{{#each callbackNumbers as |num|}}
  <li>{{num}}</li>
{{/each}}

<h5>List in callback after next runloop</h5>
{{#each syncNumbers as |num|}}
  <li>{{num}}</li>
{{/each}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}