tracked-property-index

components.my-component\.js

import Component from '@ember/component';
import EmberObject, { computed } from '@ember/object';

export default Component.extend({
  nums: undefined,
  errors: undefined,
  
  init() {
    this._super(...arguments);
    this.set('nums', [1,2,3,4,5]);
    this.set('errors', EmberObject.create());
    setTimeout(this.validateNums.bind(this), 100);
  },
  
  validateNums() {
    console.log('validating numbers');
    this.set('nums', this.nums.map((link, index) => {
      if (link % 2 === 0) {
        this.errors.set(index, 'bad number, divisible by 2');
      } else {
        this.errors.set(index, null);
      }
      return link;
    }));
  }
})

controllers.application\.js

import Controller from '@ember/controller';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>

<MyComponent/>

templates.components.my-component\.hbs

{{#each this.nums as |num index|}}
  <p>
    {{num}} : {{get this.errors index}}
  </p>
{{/each}}

---

{{#each this.nums as |num index|}}
  {{#let (get this.errors index) as |error|}}
    <p>
    	{{num}} : {{error}}
  	</p>
  {{/let}}
{{/each}}

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0"
  }
}