custom-not-custom-component

application.controller.js

import Ember from 'ember';

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

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#x-list headerText="Click Me"}}
	I am Content
{{/x-list}}

<br>
<br>

{{#x-list headerComponent="custom-header"
	headerAttrs=(hash title="Oh hai")}}
	I am Content
{{/x-list}}

custom-header.component.js

import Ember from 'ember';

const { computed } = Ember;

export default Ember.Component.extend({
  headerAttrs: null,
  
  h1: computed.readOnly('headerAttrs.title'),
  h2: computed.readOnly('headerAttrs.subtitle')
});

custom-header.template.hbs

<h1>{{h1}}</h1>

twiddle.json

{
  "version": "0.6.3",
  "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/2.4.1/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.1/ember-template-compiler.js"
  }
}

x-list-header.component.js

import Ember from 'ember';

export default Ember.Component.extend({
  text: Ember.computed.alias('headerAttrs.text')
});

x-list-header.template.hbs

{{text}}

x-list.component.js

import Ember from 'ember';

const { computed } = Ember;

export default Ember.Component.extend({
  headerComponent: 'x-list-header',
  headerText: '',
	headerAttrs: computed('headerText', function() {
  	return {
    	text: this.get('headerText')
    }
  }),
  
  isExpanded: false,
  
  actions: {
  	toggle() {
    	this.toggleProperty('isExpanded');
    }
  }
});

x-list.template.hbs

{{#if isExpanded}}
	<div class="trigger"
  	onclick={{action "toggle"}}>
		{{component
    	headerComponent
  		headerAttrs=headerAttrs}}
  </div>
  
  {{yield inverse=true}}
{{else}}
	<div class="trigger"
  	onclick={{action "toggle"}}>
  	{{component
    	headerComponent
    	headerAttrs=headerAttrs}}
  </div>
{{/if}}