Attribute Bindings

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({

  ariaControls: null,
  children: null,
  api: null,

  init() {
    this._super(...arguments);
    this.set('children', Ember.A());
    this.set('api', {
      register: this.register.bind(this),
    });
  },

  register(child) {
    this.get('children').pushObject(child);
    if (this.get('active') === child.name) {
      child.setActiveState(true);
    }
  },
  
  // observer the active property
  activateSelected: Ember.observer('active', function() {
  	let childApi = this.get('children').findBy('name', this.get('active'));
    
    this.get('children').forEach(child => child.setActiveState(false));
    
    childApi.setActiveState(true);
  }),
});

components.nested-component.js

import Ember from 'ember';

export default Ember.Component.extend({

  classNames: ['nested-component'],
  tagName: 'button',
  attributeBindings: ['ariaSelected:aria-selected', 'ariaControls:aria-controls'],

  classNameBindings: [
    'active:my-active-class:my-inactive-class',
  ],

  api: null,

  active: false,

  parentApi: null,
  
  name: null,
  
  demonstrateBug: true,
  
  ariaSelected: Ember.computed('active', 'demonstrateBug', function() {
    if (this.get('demonstrateBug')) {
      return this.get('active');
    }
    return this.get('active') ? 'true' : 'false';
}),

  init() {
    this._super(...arguments);
    Ember.assert('name required', this.get('name'));
    this.set('api', {
      name: this.get('name'),
      setActiveState: this.setActiveState.bind(this),
    });
    this.get('parentApi').register(this.get('api'));
  },

  setActiveState(value) {
    this.set('active', Boolean(value));
  },
  
  click() {
    this.get('onselect')(this.get('name'));
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  active: 'first',
  showBug: true,
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

.nested-component {
  position: relative;
  padding: 20px;
  margin: 20px;
  background-color: transparent;
}

.nested-component[aria-selected=""] {
  background-color: yellow;
}
.nested-component[aria-selected="true"] {
  background-color: green;
  color: yellow;
}
.nested-component[aria-selected="false"] {
  background-color: blue;
  color: while;
}

.nested-component.my-active-class {
  border: 10px solid green;
}

.nested-component.my-active-class:before {
  position: absolute;
  display: block;
  content: '⇩ Active ⇩';
  top: -40px;
  left: 0;
  background-color: green;
  color: yellow;
  
}
.nested-component[aria-selected=""]:after {
  position: absolute;
  display: block;
  white-space: nowrap;
  content: '⇧ aria-selected=""';
  bottom: -40px;
  left: 0;
  background-color: green;
  color: yellow;
}
.nested-component.my-inactive-class {
  border: 10px solid blue;
}

templates.application.hbs

<h1>Demonstrating a regression with attribute binding</h1>

<p>
Regression starts with ember 2.7.
</p>

<p>
If the "active" object has a GREEN background, it works. if the "active" object has a YELLOW backgrond, it's broken.

<pre>.nested-component[aria-selected="true"] {
  background-color: green;
  color: yellow;
}</pre>
</p>
<p></p>

<p>Demonstrate Bug? {{input type='checkbox' checked=showBug}}</p>

{{#my-component
		active=(readonly active)
    onselect=(action (mut active))
    as |foo|
}}
   {{#foo.nested demonstrateBug=showBug name='first'}}First{{/foo.nested}}
   {{#foo.nested demonstrateBug=showBug name='second'}}Second{{/foo.nested}}
{{/my-component}}
<br>
<br>

templates.components.my-component.hbs

{{yield (hash
						nested=(component 'nested-component'
  									parentApi=api
          					onselect=(action onselect)
          				)
   			)
}}

templates.components.nested-component.hbs

{{yield}}

tests.helpers.destroy-app.js

import Ember from 'ember';

export default function destroyApp(application) {
  Ember.run(application, 'destroy');
}

tests.helpers.resolver.js

import Resolver from '../../resolver';
import config from '../../config/environment';

const resolver = Resolver.create();

resolver.namespace = {
  modulePrefix: config.modulePrefix,
  podModulePrefix: config.podModulePrefix
};

export default resolver;

tests.helpers.start-app.js

import Ember from 'ember';
import Application from '../../app';
import config from '../../config/environment';

const { run } = Ember;
const assign = Ember.assign || Ember.merge;

export default function startApp(attrs) {
  let application;

  let attributes = assign({rootElement: "#test-root"}, config.APP);
  attributes = assign(attributes, attrs); // use defaults, but you can override;

  run(() => {
    application = Application.create(attributes);
    application.setupForTesting();
    application.injectTestHelpers();
  });

  return application;
}

tests.test-helper.js

import resolver from './helpers/resolver';
import {
  setResolver
} from 'ember-qunit';

setResolver(resolver);

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "beta",
    "ember-data": "2.8.0",
    "ember-template-compiler": "beta",
    "ember-testing": "beta"
  },
  "addons": {}
}