Use computed or not

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  showInput: true,
  
  numbers: Ember.computed(() => [1,2,3]),
  
  instanceNumber: 0,
  
  actions: {
    changeArray() {
    	this.set('numbers', [4,5,6]);
    },
    changeNumbers() {
      let instanceNum = this.get('instanceNumber');
      instanceNum = instanceNum + 1;
      this.set('instanceNumber', instanceNum);
    }
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
	{{my-component}}
<br>
	{{my-component}}
<br>

templates.components.my-component.hbs

My Component {{instanceNumber}}
{{#if showInput}}
	<div>
		<input type="text" name="username" value={{numbers}}/>
  </div>
{{/if}}
<button type="button" {{action "changeNumbers"}}>Change Numbers</button>
<button type="button" {{action "changeArray"}}>Change array</button>

twiddle.json

{
  "version": "0.11.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.10.2",
    "ember-data": "2.11.0",
    "ember-template-compiler": "2.10.2",
    "ember-testing": "2.10.2"
  },
  "addons": {}
}