backbone-relation

Backbone does not support relations by default. This is a simple package that adds relations to Backbone.

The idea is simple: you can define relations like you define defaults. A relation can be either a Model or a Collection and attributes can be set recursively through the parent.

Why use this over backbone-relational? We found backbone-relational too complex. Itʼs basically an ORM in the frontend. We didnʼt need that, hence this package.

Vision

• 100% compatible with original Backbone codebase. All Backbone test must pass when tested using backbone-relation.
• Extend Backbone, don't patch it.
• Make it clear. Only add well defined and tested features, leaving as little as possible open to interpretation.

Use case

Imagine an API-endpoint gives the following response when hitting api/user/1:

{
    id: 1,
    username: 'witchhunter',
    profile: {
        id: 7,
        first_name: 'Michelle',
        last_name: 'Velvet'
    }
}

You can define 2 models, one called MProfile and the other MUser:

MProfile = MRelation.extend();

MUser = MRelation.extend({
    relations: {
        profile: MProfile
    }
})

Now you can do a fetch and the profile model will be filled with data on the user model:

mUser = new MUser({id: 1});
mUser.fetch();

... 

mUser.get('profile').get('first_name'); // 'Michelle'

When setting data, you can do the following:

mUser.set({
    profile: {first_name: 'Vera'}
});

mUser.get('profile').get('first_name'); // 'Vera'

Defining relations

You can define relations using the relations attribute. It can either be a hash or a function that returns a hash. There are a few different ways to define relations:

Simple

The simplest form without any options. Example:

var MAuthor = Model.extend({
    relations: {
        // This is a simple relation where MUser is a Model.
        user: MUser,

        // Here we define an attribute which should be a collection.
        posts: CPost,
    }
})

Advanced

With this form you can add a bit more configuration options. These are the options at the moment:

Key	Description
relationClass	The constructor for the relation. This can either be a Backbone.Model or a Backbone.Collection.

Example:

var MAuthor = Model.extend({
    relations: {
        // Similar to posts, just another syntax. This supports more complex configuration options.
        contacts: {relationClass: CContact}
    }
})

Setting related data

The most basic form of setting a related data is getting it first:

mAuthor.get('user').set('id', 17);
mAuthor.get('contacts').set([{id: 1}, {id: 2}]);

Another way of setting related data is using the attribute name on the parent. These lines do exactly the same:

mAuthor.get('user').set('id', 17);
mAuthor.set('user', {id: 17});
mAuthor.set({user: {id: 17}});

This implies that once a relation is set, it cannot be overridden with another value. If you do really want to set another instance for a relation, then first use unset:

mAuthor.unset('user');
mAuthor.set('user', mUser);

Bottom line: if a relation exists, set is proxied.

Getting related data

You can use vanilla Backbone to get related data:

mAuther.get('user'); // -> Instance of MUser.
mAuther.get('user').get('id') // -> Get the id of the related user.

Model.dot

Shorthand for getting nested attributes. Example:

model
    .get('nestedModel1')
    .get('nestedCollection2')
    .get('nestedIdOfModel3')
    .get('foo');

can be written like:

model.dot('nestedModel1.nestedCollection2.nestedIdOfModel3.foo');

This depends on that the nested relation has a get function defined. That function is called each time a dot is found. If you try to use dot on a value that does not have the function get defined, it will return undefined.

Returns undefined because of someString is a string without a get function defined:

model.dot('nestedModel1.someString.foo.bar');

Returns undefined because of object is an object without a get function defined:

model.dot('nestedModel1.object.foo.bar');

Returns undefined because of nonExistingModelOrCollection is undefined and thus without a get function defined:

model.dot('nestedModel1.nonExistingModelOrCollection.foo.bar');

Returns undefined because of nonExistingId is undefined and thus without a get function defined:

model.dot('nestedCollection1.nonExistingId.foo.bar');

Itʼs not possible to retrieve attributes with a . in the name. You can use get instead:

model.dot('nestedModel1.nestedCollection2.nestedIdOfModel3').get('foo.bar');

Options

Key	Default	Description
createRelations	true	true: create relations while initializing model. false: skip creating relations upon initialization.