Conditionally rendered components

components.hider-component.js

import Ember from 'ember';
import through from '../indirect';
// Inlined, since no addons in twiddles. Really use this:
// import through from 'ember-computed-indirect/utils/indirect';

export default Ember.Component.extend({
  user: Ember.inject.service('user-permissions'),
  flagName: '', // specify in extending component
  flagPath: Ember.computed('flagName', function() {
		return 'user.' + this.get('flagName');
  }),
  flagStatus: through('flagPath'),
  isVisible: Ember.computed.readOnly('flagStatus')
});

components.sometimes-feature.js

import Ember from 'ember';
import HiderComponent from './hider-component';

export default HiderComponent.extend({
  flagName: 'hasFeature'
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
	user: Ember.inject.service('user-permissions'),
  appName: 'Ember Twiddle',
  actions: {
    toggleVisibility() {
      this.toggleProperty('user.hasFeature');
    }
  }
});

indirect.js

import Ember from 'ember';

var get = Ember.get;
var set = Ember.set;

export default function indirect(pathProperty) {

  return Ember.computed(pathProperty, {
    get: function getIndirectPropertyValue(key) {

      var metaSourceKey = 'source.' + key;
      var metaObserverKey = 'observer.' + key;
      // Use a Ember.meta instead of storing meta info on the object itself
      var _meta = Ember.meta(this, true);
      _meta = _meta.__indirect__ || (_meta.__indirect__ = {});

      var metaObserver = _meta[metaObserverKey];
      if (!metaObserver) {
        _meta[metaObserverKey] = metaObserver = function() {
          this.notifyPropertyChange(key);
        };
      }

      var currentKey = get(this, pathProperty);
      if (currentKey !== _meta[metaSourceKey]) {
        if (_meta[metaSourceKey]) {
          Ember.removeObserver(this, _meta[metaSourceKey], this, metaObserver);
        }
        if (currentKey) {
          Ember.addObserver(this, currentKey, this, metaObserver);
        }
        _meta[metaSourceKey] = currentKey;
      }

      return currentKey && get(this, currentKey);
    },

    set: function setIndirectPropertyValue(key, value) {
      return set(this, get(this, pathProperty), value);
    }
  });
}

services.user-permissions.js

import Ember from 'ember';

export default Ember.Service.extend({
  hasFeature: true
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
<button {{action "toggleVisibility"}}>Toggle feature</button>
<br>
{{sometimes-feature}}
<br>

templates.components.sometimes-feature.hbs

The feature's "{{user.hasFeature}}"

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}