named yields

components.page-layout.js

import Ember from 'ember';

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

components.render-slot.js

import { computed } from "@ember/object";
import Ember from 'ember';

const RenderSlot = Ember.Component.extend({

  slotName: "",
  currentYield: "",
  
  shouldRender: computed("slotName", "currentYield", function () {
    return this.slotName && this.slotName === this.currentYield;
  })

});

RenderSlot.reopenClass({
  positionalParams: ['slotName', 'currentYield']
});


export default RenderSlot;

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

{{#page-layout as | slot | }}
	
  {{#render-slot "header" slot}}
  	This is the header!
  {{/render-slot}}

  {{#render-slot "body" slot}}
  	Here's some content for the body
  {{/render-slot}}

  {{#render-slot "footer" slot}}
  	Don't forget the footer!
  {{/render-slot}}

{{/page-layout}}

templates.components.page-layout.hbs

<h1>{{yield "header"}}</h1>
<p>{{yield "body"}}</p>
<br><br>
<br><br>
<br><br>
<small>{{yield "footer"}}</small>

templates.components.render-slot.hbs

{{#if shouldRender}}
	{{yield}}
{{/if}}

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}