Double each - dynamic binding

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  rows: [],
  headers: [],
  
  header1: 'title',
  header2: 'description',
  
  onHeadersChange: Ember.observer('header1', 'header2', function() {
    let headers = [
    	this.get('header1'),
      this.get('header2')
    ];
    
    let rows = [{
      title: '',
      description: ''
    }];
    
    this.setProperties({
      headers,
      rows
    });
  }).on('init')
});

application.template.hbs

Header 1: {{input type="text" value=header1}}
Header 2: {{input type="text" value=header2}}

<hr />
<table>
    <thead>
        <tr>
            {{#each headers as |h|}}
                <th>{{h}}</th>
            {{/each}}
        </tr>
    </thead>
    <tbody>
    	{{#each rows as |r|}}
        <tr>
            {{#each headers as |h|}}
                <td>
                  <input onkeyup={{action (mut (get r h)) value="target.value"}}>
                  </td>
            {{/each}}
        </tr>
    	{{/each}}
    </tbody>
</table>
<hr />
<h3>Rows</h3>
{{#each rows as |r|}}
  {{#each headers as |h|}}
    Row[{{h}}]: {{get r h}}<br/>
  {{/each}}
{{/each}}

twiddle.json

{
  "version": "0.6.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.3.1/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.3.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}