bind to child view

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
});
 

application.template.hbs

{{parent-component}}

child-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  childComponentProp: null,
  
  actions: {
    set: function() {
    	this.attrs.childComponentProp.update(3);  
    },
    unset: function() {
    	this.attrs.childComponentProp.update(null);  
    }
  }
});

child-component.template.hbs

child-component: {{childComponentProp}}
<br />
<button {{action 'set'}}>Set</button>
<button {{action 'unset'}}>Unset</button>

parent-component.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNameBindings: ['computedClasses'],
  
	childComponentProp: null,
  
  computedClasses: function() {
	  var classes = '';
    // some other stuff
    if(this.get('childComponentProp') === 3) {
      classes = classes + ' some-class';
    }
    return classes.trim();
  }.property('childComponentProp'),
});

parent-component.template.hbs

parent-component: {{childComponentProp}}
<br>
{{component "child-component" childComponentProp=(mut childComponentProp)}}

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.some-class {
  color: blue
}

twiddle.json

{
  "version": "0.6.0",
  "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"
  }
}