dirty-helpers.js

import Ember from 'ember';
export { dirtyHasMany, dirtyBelongsTo, dirtyMixin };

var dirty = 'relationshipIsDirty';

function dirtyMixin (obj) {
  var args = Object.keys(obj);
  var comp = Ember.computed;
  args.push('isDirty');
  obj[dirty] = comp.any.apply(comp, args);
  return Ember.Mixin.create(obj);
}

function dirtyHasMany (name) {
  return function () {
    if (this.get('_data.' + name + '.length') !== this.get(name + '.length')) {
      return true;
    }
    return this.get(name).any(function (item) {
      return item.get(dirty);
    });
  }.property(name + '.@each.' + dirty, name + '.length');
}

function dirtyBelongsTo (name) {
  return function () {
    return this.get('_data.' + name + '.id') !== this.get(name + '.id');
  }.property(name);
}

drink-ingredient.js

import DS from 'ember-data';
import { dirtyBelongsTo, dirtyMixin } from './dirty-helpers';

var attr = DS.attr, belongsTo = DS.belongsTo;

var mixin = dirtyMixin({
  _isIngredientDirty: dirtyBelongsTo('ingredient')
});

export default DS.Model.extend(mixin, {
  amount: attr('number'),
  ingredient: belongsTo('ingredient'),
  drink: belongsTo('drink')
});

drink.js

import DS from 'ember-data';
import { dirtyHasMany, dirtyBelongsTo, dirtyMixin } from './dirty-helpers';

var attr = DS.attr, hasMany = DS.hasMany, belongsTo = DS.belongsTo;

var mixin = dirtyMixin({
  _areDrinkIngredientsDirty: dirtyHasMany('drinkIngredients'),
  _areDrinkGarnishesDirty: dirtyHasMany('drinkGarnishes'),
  _isGlassDirty: dirtyBelongsTo('glass')
});

export default DS.Model.extend(mixin, {
  name: attr('string'),
  drinkIngredients: hasMany('drink-ingredient'),
  drinkGarnishes: hasMany('drink-garnish'),
  glass: belongsTo('glass')
});