DS#hasMany()

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

DS.hasMany 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.
• inverse: A string used to identify the inverse property on a related model.

One-To-Many

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

import DS from 'ember-data';

export default DS.Model.extend({
  comments: DS.hasMany('comment')
});

import DS from 'ember-data';

export default DS.Model.extend({
  post: DS.belongsTo('post')
});

Many-To-Many

To declare a many-to-many relationship between two models, use DS.hasMany:

import DS from 'ember-data';

export default DS.Model.extend({
  tags: DS.hasMany('tag')
});

import DS from 'ember-data';

export default DS.Model.extend({
  posts: DS.hasMany('post')
});

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

import DS from 'ember-data';

export default DS.Model.extend({
  tags: DS.hasMany()
});

will lookup for a Tag type.

Explicit Inverses

Ember Data will do its best to discover which relationships map to one another. In the one-to-many code above, for example, Ember Data can figure out that changing the comments relationship should update the post relationship on the inverse because post is the only relationship to that model.

However, sometimes you may have multiple belongsTo/hasManys for the same type. You can specify which property on the related model is the inverse using DS.hasMany's inverse option:

import DS from 'ember-data';

export default DS.Model.extend({
  onePost: DS.belongsTo('post'),
  twoPost: DS.belongsTo('post'),
  redPost: DS.belongsTo('post'),
  bluePost: DS.belongsTo('post')
});

import DS from 'ember-data';

export default DS.Model.extend({
  comments: DS.hasMany('comment', {
    inverse: 'redPost'
  })
});

You can also specify an inverse on a belongsTo, which works how you'd expect.