ember-filter-async-relationship

application.controller.js

import Ember from 'ember';

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

application.template.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
User: {{model.username}}
<br>
<br>
{{#each model.indexFields as |field|}}
	{{field.label}}: {{field.value}}
{{/each}}

models.custom-field-position.js

import DS from 'ember-data';

export default DS.Model.extend({
  order: DS.attr('number'),
  tab: DS.belongsTo('custom-field-tab', {async: true})
});

models.custom-field-tab.js

import DS from 'ember-data';

export default DS.Model.extend({
  slug: DS.attr('string'),
  label: DS.attr('string'),
  icon: DS.attr('string'),
  order: DS.attr('number')
});

models.custom-field.js

import DS from 'ember-data';

export default DS.Model.extend({
  label: DS.attr('string'),
  
  positions: DS.hasMany('custom-field-position', {async: false})
});

models.user-custom-field.js

import DS from 'ember-data';

export default DS.Model.extend({
  value: DS.attr('string'),
  field: DS.belongsTo('custom-field', {async: false})
});

models.user.js

import DS from 'ember-data';

const User = DS.Model.extend({
  username: DS.attr('string'),
  
  customFields: DS.hasMany('user-custom-field', {async: false}),
  
  indexFields: function() {
  	return this._filterByTab(1);
  }.property('customFields.[]'),
  
  contactFields: function() {
  	return this._filterByTab(2);
  }.property('customFields.[]'),
  
  _filterByTab: function(tab) {
    return this.get('customFields').filter(function(field) {
      var position = field.get('field.positions').findBy('tab.id', '' + tab);
      if (! position) {
        return false;
      }
      field.order = position.get('order');
      return true;
    }).sortBy('order');
  }
});

return User;

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model: function() {
    return this.store.find('user', 1);
  }
});

twiddle.json

{
  "version": "0.4.16",
  "EmberENV": {
    "FEATURES": {}
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.1.0",
    "ember-data": "2.1.0",
    "ember-template-compiler": "2.1.0"
  }
}