setter till 1.12

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  actions: {
    updateAttr() {
      this.set('otherattr', Math.random());
    }
  }
});

application.template.hbs

<h1>1.12 setter</h1>
<br>
<br>
{{some-comp ottherattr=otherattr setterattr=setterattr}}
<button {{action "updateAttr"}}>update otherattr</button>
<br>
<br>

some-comp.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  otherattr: null,
  
  setterattr: Ember.computed({
    get() {
      return 'anything';
    },
    set(key, value) {
      this.set('datestamp', Date.now());
    }
  })
});

some-comp.template.hbs

Datestamp (updated in setterattr): {{datestamp}}
<br />
<br />

twiddle.json

{
  "version": "0.4.16",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.12.1/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.1.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.12.1/ember-template-compiler.js"
  }
}