Named Positional Parameters

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName:'Ember Twiddle',
  
  currentBooleanValue: true,
  
  actions: {
    toggleIf() {
      this.toggleProperty('currentBooleanValue');
      return false;
    }
  }
});

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
{{#my-if currentBooleanValue}}
  This is true
{{ else }}
  This is false
{{/my-if}}

<button {{action 'toggleIf'}}>
  Toggle if
</button>
<br>
<br>

my-if.component.js

import Ember from 'ember';

const { computed } = Ember;

const MyIfComponent = Ember.Component.extend({
});

MyIfComponent.reopenClass({
  positionalParams: ['predicateValue']
});

export default MyIfComponent;

my-if.template.hbs

{{#if predicateValue}}
  Yay!
  {{yield}}
{{ else }}
  😢
	{{yield to="inverse"}}
{{/if}}

twiddle.json

{
  "version": "0.4.17",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.2.0/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}