emberjs-rolling-back-belongs-to.md

EmberJs Rolling Back Belongs To

I've been doing this with Ember-Data-2.13 that is interacting with a Rails JSONAPI-Resources backend.

Ember Data's rollbackAttributes() on a model does a great job of rolling back any attributes that were modified.

The belongs-to relationships however, these require some extra love. Here's what I've done; it's pretty simple:

1. Override the model's rollbackAttributes() to also call a new function named rollbackBelongsTo().
2. Also on your model, author a function named preserveBelongsTo().
   This function manually caches the instances assigned to the belongs-to relationship.
3. Finally on your model, author the rollbackBelongsTo() mentioned first.

Here's a simple example of a very basic user model:

// app/models/user.js

export default DS.Model.extend({
  /* ---------------------------------------------------------- ROLLBACK HACK */

  /**
   * Call this function from your component/route immediately
   * prior to editing.
   */
  preserveBelongsTo() {
    this.set('preserved', Ember.Object.create({
      telCountryCode: this.get('telCountryCode.content')
    }));
  },
  /**
   * Override the basic rollbackAttribute(); in addition call the
   * `rollbackBelongsTo()` function.
   * @override
   */
  rollbackAttributes() {
    this._super(...arguments);
    this.rollbackBelongsTo();
  },
  /**
   * Rollback the `belongs-to` relationships.
   */
  rollbackBelongsTo() {
    if (Ember.isPresent(this.get('preserved'))) {
      this.set('telCountryCode', this.get('preserved.telCountryCode'));
    }
  },

  /* ------------------------------------------------------------- PROPERTIES */

  email: DS.attr('string'),
  familyName: DS.attr('string'),
  givenName: DS.attr('string'),
  telNational: DS.attr('string'),

  /* ---------------------------------------------------------- RELATIONSHIPS */

  telCountryCode: DS.belongsTo('phone-country-code')
})

WhyTF Questions...

---

Why aren't you using Ember-Data's Model events (e.g. rolledBack)?

It would be great to bind to the Model's rolledBack event in an effort to trigger the rolling back of the belongs-to relationships.

In addition, using the Model's didLoad and didUpdate events to cache the belongs-to relationship values would make life so easy.

Alas, there are too many bugs in Ember-Data for this to work perfectly. For example, I cannot even get the rolledBack event to fire in regular circumstances.

Why not use the Model's relationships computed property to dynamically cache the belongs-to relationships?

I'm thinking doing just that.

Why don't you use the ember-rollback-relationships add-on?