Ember Managed Relationships

This ember addons tries to solve the problem, that ember-data is not handling relationship management out of box very good.

In Ember.js it is possible to define hasMany and belongsTo relationships, but is not possible to allow ember to track relationship status out of box. Just some of the problems of ember relationship management

• Ember is not capable to track whether a child model is dirty and is not dirtiing a parent model
• In meber it is not possible track whether the belongsTo has changed or not
• Rollback is not working as expected
• ...

How is this working

Basically there are 3 types of relationships:

Referenced relationships

These relationships are most common, what really happens here is that we want to check wheather a reference to the model has changed, while we dont really care wheather the referced model has really changed

Subject = Model.extend(Managed, {
    name: attr('string')
})

Student = Model.extend(Managed, {
   favouriteSubject: belongsTo('subject', {referenced: true})
})

student.get('favoriteSubject.id') == 1 //true
student.get('isDirty') // false

student.set('favoriteSubject', secondSubject) // has id '2' 
student.get('isDirty') // true - the reference to the favoriteSubject has changed
-------------------------------
student2.get('favoriteSubject.name') == 'Math' //true
student2.get('isDirty') // false

favoriteSubject = student2.get('favoriteSubject');
favoriteSubject.get('isDirty') // false

favoriteSubject.set('name', 'English') //Setting different name
favoriteSubject.get('isDirty') // true - the value has changed

student2.get('isDirty') // false - the reference to the favoriteSubject has not changed 

Managed relationships

These are the relationships when we are interested to know wheather not just the references have changed, but are interested in the changed happening on objects too

Subject = Model.extend(Managed, {
    name: attr('string')
})

Student = Model.extend(Managed, {
   favouriteSubject: belongsTo('subject', {managed: true})
})

student2.get('favoriteSubject.name') == 'Math' //true
student2.get('isDirty') // false

favoriteSubject = student2.get('favoriteSubject');
favoriteSubject.get('isDirty') // false

favoriteSubject.set('name', 'English') //Setting different name
favoriteSubject.get('isDirty') // true - the value has changed

student2.get('isDirty') // true - the reference to the favoriteSubject has not changed, but the value has changed and this dirties the whole parent model

-------------------------------

student.get('favoriteSubject.id') == 1 //true
student.get('isDirty') // false

student.set('favoriteSubject', secondSubject) // has id '2' 
student.get('isDirty') // true - the reference to the favoriteSubject has changed - managed models take into account refence changes too

ReadOnly relationships

In thesee relationships we dont care if the relationship changes or not

How to use

Right now it is not possible to install the addon throu ember:install, so if you would like to use this just insert a line to your package.json pointing to master or a tag in this repository

Mixin

Just add the mixin to the model where you want to have use the functionality

import DS from 'ember-data';
import ManagedMixin from 'ember-managed-relationships/managed-relationships-mixin';

export default DS.Model.extend(ManagedMixin, {
...
});

Options

These options could be used in the options hash to hasMany() and belongsTo() definitions

• referenced:true - a referenced relationship
• managed: true - a managed relationship
• ordered: true - when the order of the hasMany relationship matters
• noCommitNew: true - when we dont want to commit a relationship to the store, after it is created on backend, because we are removing it manually, only for hasMany

Default API changes

.isDirty and rollback() will be defined on every Model.

isDirty

• The defaultly isDirty property is defined as a computed property, which returns the value of hasDirtyAttributes property

rollback

• rollback() on the model will defaultly call the this.rollbackAttributes() on the model

Limitation

This plugin is not solving how to handle creation of new 'managed' models as Ember is not capable mapping newly created models, to models with ids. They are multiple ways how to solve this:

1. For the managed models use UUID as id so you can generate id's on frontend
2. unload the newly created models after save from the store ...

Info

This package is soon going to be moved and this package will be deprecated so please check back for updates