Notifying children of object property changes

components.item-list.js

import Ember from 'ember';

export default Ember.Component.extend({
  items: ['hello', 'world'],
  
  displayedItems: Ember.computed('visibilityMap', 'items', function () {
		const visibilityMap = this.get('visibilityMap');
    const items = this.get('items');

    return items.filter(item => {
      return visibilityMap.get(item) !== false;
    });
  }),
});

components.item-manager.js

import Ember from 'ember';

export default Ember.Component.extend({
  init() {
    this._super(...arguments);
    this.visibilityMap = new Map();
  },
  
  actions: {
    hide(item) {
      const visibilityMap = this.get('visibilityMap');
      visibilityMap.set(item, false);
      this.notifyPropertyChange('visibilityMap');
    },
  },
});

controllers.application.js

import Ember from 'ember';

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

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{#item-manager
	as |visibilityMap hide|
}}
  <button {{action hide 'hello'}}>Hide hello</button>
	{{item-list visibilityMap=visibilityMap}}
{{/item-manager}}
<br>
<br>

templates.components.item-list.hbs

{{#each displayedItems as |item|}}
  {{item}}
{{/each}}

templates.components.item-manager.hbs

{{yield	visibilityMap (action 'hide')}}

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"
  }
}