Function

belongsTo (modelName, options) Ember.computed public

Module:	@ember-data/model

Defined in ../model/addon/-private/belongs-to.js:13

modelName

String

(optional) type of the relationship

options

Object

(optional) a hash of options

returns

Ember.computed

relationship

belongsTo is used to define One-To-One and One-To-Many relationships on a Model.

belongsTo takes an optional hash as a second parameter, currently supported options are:

• async: A boolean value used to explicitly declare this to be an async relationship. The default is true.
• inverse: A string used to identify the inverse property on a related model in a One-To-Many relationship. See Explicit Inverses
• polymorphic A boolean value to mark the relationship as polymorphic

One-To-One

To declare a one-to-one relationship between two models, use belongsTo:

import Model, { belongsTo } from '@ember-data/model';

export default class UserModel extends Model {
  @belongsTo('profile') profile;
}

import Model, { belongsTo } from '@ember-data/model';

export default class ProfileModel extends Model {
  @belongsTo('user') user;
}

One-To-Many

To declare a one-to-many relationship between two models, use belongsTo in combination with hasMany, like this:

import Model, { hasMany } from '@ember-data/model';

export default class PostModel extends Model {
  @hasMany('comment') comments;
}

import Model, { belongsTo } from '@ember-data/model';

export default class CommentModel extends Model {
  @belongsTo('post') post;
}

You can avoid passing a string as the first parameter. In that case Ember Data will infer the type from the key name.

import Model, { belongsTo } from '@ember-data/model';

export default class CommentModel extends Model {
  @belongsTo post;
}

will lookup for a Post type.

Sync relationships

Ember Data resolves sync relationships with the related resources available in its local store, hence it is expected these resources to be loaded before or along-side the primary resource.

import Model, { belongsTo } from '@ember-data/model';

export default class CommentModel extends Model {
  @belongsTo('post', {
    async: false
  })
  post;
}

In contrast to async relationship, accessing a sync relationship will always return the record (Model instance) for the existing local resource, or null. But it will error on access when a related resource is known to exist and it has not been loaded.

let post = comment.get('post');