attr_bindings_2

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

application.template.hbs

<br>
{{my-component rows=4}}
{{my-component}}

<br>
{{outlet}}
<br>
<br>

my-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  tagName: 'textarea',
  attributeBindings: ['rows'],
  rows: 2, 

  input(event) {
    let value = event.target.value;
    this.set('rows', isNaN(value)? 2 : value);
  }
});

my-component.template.hbs

{{rows}}

twiddle.json

{
  "version": "0.6.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "1.13.13",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.0/ember-data.js",
    "ember-template-compiler": "1.13.13"
  }
}