Child vs Parent Render

components.child-bool.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNames:['child-component'],
  init(){
    this._super(...arguments)
    console.log(`hello from ${this}`)
  },
});

components.parent-bool.js

import Ember from 'ember';

export default Ember.Component.extend({
  classNames:['child-component'],
  init(){
    this._super(...arguments)
    console.log(`hello from ${this}`)
  }
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Conditional Rendering in Child vs Parent</h1>

<p>"child-bool" will always render and lifecylce methods even get called when you don't want them because the parent instantiated it. But "parent-bool" does not until the parent boolean toggles and instantiates the component render. You can see the effect of this by:</p>

<ol>
	<li>Look at the console and see that child-bool console logs are printed even when the component isn't visible</li>
  <li>Open Elements in devtools and see that the class "child-component" is in the DOM 1 time when child compoents should not be rendered and twice when they should be. Child-bool is always rendered! </li>
</ol>

<h2>With conditional in component</h2>
<ChildBool
	@show={{this.showChild}}
/>

<h2>With conditional in parent</h2>
{{#if this.showChild}}
	<ParentBool/>
{{/if}}

<label for='c'>Show Child Components</label>
{{input 
	id='c'
	type='checkbox' 
  checked=showChild
  onChange=(mut showChild)
}}

{{outlet}}

templates.components.child-bool.hbs

{{#if this.show}}
	<p data-experiment="child">child component</p>
  {{this.someComputed}}
{{/if}}

templates.components.parent-bool.hbs

<p data-experiment="child">child component</p>

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"
  }
}