child component rendering

components.child-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  
  classNames: [ 'child-component' ],
  
  didRender () {
  	console.log('%cchild-component::didRender', 'background-color: fuchsia; color: black;')
  }
  
});

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  
  classNames: [ 'my-component' ],
  
  classNameBindings: [ 'foo' ],
  
  didRender () {
  	console.log('%cmy-component::didRender', 'background-color: black; color: yellow;')
  }
  
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  actions: {
  	updateFoo () {
    	this.toggleProperty('foo');
    }
  }
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}
.my-component {
  background-color: lightgray;
  border: solid 1px darkgray;
  border-radius: 3px;
}
.my-component.foo {
	background-color: gray;
}
.child-component {
  margin: 10px auto;
	width: 400px;
  height: 200px;
  background-color: yellow;
  border: solid 1px gray;
  border-radius: 3px;
}

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<button type="button" {{action "updateFoo"}}>Update Foo</button>
<br>

{{my-component foo=foo}}

templates.components.child-component.hbs

{{yield}}

templates.components.my-component.hbs

{{child-component}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}