backbone-rel

v0.10.11

Relationships between Backbone models in the flavor of MongoDB's document references and embeddings

backbone extension relations relationships embeddings references

References vs. Embeddings

backbone-rel extends Backbone by two concepts that allow applications to model relationships between models: references and embeddings. These concepts are inspired by the MongoDB data modeling in terms of embedded and referenced documents (http://docs.mongodb.org/manual/core/data-modeling-introduction/).

References

A reference describes a relationship between two model classes (A and B) in terms of a unidirectional link or pointer from one instance of A to one or many instances of B. The reference is defined on the referencing object using the ID of the referenced object.

var User = Backbone.Model.extend({});

var LikeCollection = Backbone.Collection.extend({
    model: Like
});

var Comment = Backbone.Model.extend({
    references: {
        author: User,           // to-one reference
        likes: LikeCollection	// to-many reference
    }
});

References work especially well in conjunction with https://github.com/disqus/backbone.uniquemodel. If you set up a reference to a model class tracked by backbone.uniquemodel, a referenced model instance will automatically be resolved to the right instance in the unique model cache.

var User = UniqueModel( Backbone.Model.extend({}), "User" );

var Comment = Backbone.Model.extend({
    references: {
        author: User
    }
});
var user = new User({ id: 1, name: "John Doe" });
var comment = new Comment({ authorId: 1 });
assert(comment.get("user") === user);  // the referenced author has been resolved to the unique user instance

Embeddings

An embedded object lives in its parent.

The URL for the API endpoint of the embedded object is built based on the parent model's URL by appending the embedded object's "urlSuffix" property.
Alternatively, the embedded object can be managed entirely through its parent, meaning that it does not have a dedicated URL endpoint but its JSON representation is inlined in the parent JSON.

var MetaData = Backbone.Model.extend({});

var CommentCollection = Backbone.Collection.extend({
    model: Comment
});

var Post = Backbone.Model.extend({
    embeddings: {
        meta: MetaData,				// to-one embedding
        comments: CommentCollection // to-many embedding
    }
})