Customizing Adapters

Customizing Adapters

In Ember Data, the Adapter determines how data is persisted to a backend data store, such as the URL format and headers for a REST API. (The format of the data itself is determined by the serializer.) Ember Data's default Adapter has some built-in assumptions of how a REST API should look. If your backend conventions differ from these assumptions Ember Data makes it easy to change its functionality by swapping out or extending the default Adapter.

Some reasons for customizing an Adapter include using underscores_case in your urls, using a medium other than REST to communicate with your backend API or even using a local storage backend.

Extending Adapters is a natural process in Ember Data. Ember takes the position that you should extend an adapter to add different functionality. This results in code that is more testable, easier to understand and reduces bloat for people who may want to subclass your adapter.

If your backend has some consistent rules you can define an adapter:application. The adapter:application will get priority over the default Adapter, however it will still be superseded by model specific Adapters.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  // Application specific overrides go here
});

If you have one model that has exceptional rules for communicating with its backend than the others you can create a Model specific Adapter by running the command ember generate adapter adapter-name. For example, running ember generate adapter post will create the following file:

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  namespace: 'api/v1'
});

By default Ember Data comes with several built-in adapters. Feel free to use these adapters as a starting point for creating your own custom adapter.

• DS.Adapter is the basic adapter with no functionality. It is generally a good starting point if you want to create an adapter that is radically different from the other Ember adapters.

• DS.JSONAPIAdapter The JSONAPIAdapter is the default adapter and follows JSON API conventions to communicate with an HTTP server by transmitting JSON via XHR.

• DS.RESTAdapter The RESTAdapter allows your store to communicate with an HTTP server by transmitting JSON via XHR. Before Ember Data 2.0 this adapter was the default.

Customizing the JSONAPIAdapter

The DS.JSONAPIAdapter has a handful of hooks that are commonly used to extend it to work with non-standard backends.

URL Conventions

The JSONAPIAdapter is smart enough to determine the URLs it communicates with based on the name of the model. For example, if you ask for a Post by ID:

store.findRecord('post', 1).then(function(post) {
});

The JSON API adapter will automatically send a GET request to /posts/1.

The actions you can take on a record map onto the following URLs in the JSON API adapter:

Pluralization Customization

To facilitate pluralizing model names when generating route urls Ember Data comes bundled with Ember Inflector, an ActiveSupport::Inflector compatible library for inflecting words between plural and singular forms. Irregular or uncountable pluralizations can be specified via Ember.Inflector.inflector. A common way to do this is:

// sets up Ember.Inflector
import './models/custom-inflector-rules';

import Inflector from 'ember-inflector';

const inflector = Inflector.inflector;

inflector.irregular('formula', 'formulae');
inflector.uncountable('advice');

// Meet Ember Inspector's expectation of an export
export default {};

This will tell the JSON API adapter that requests for formula should go to /formulae/1 instead of /formulas/1, and that requests for advice should go to /advice/1 instead of /advices/1.

When specifying irregular inflection rules for compound words, only the final word or phrase should be specified. For example, to specify the plural of redCow as redKine or red-cow as red-kine, only the final word segments cow and kine should be specified:

inflector.irregular('cow', 'kine');

Endpoint Path Customization

The namespace property can be used to prefix requests with a specific url namespace.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  namespace: 'api/1'
});

Requests for person would now target http://emberjs.com/api/1/people/1.

Host Customization

By default the adapter will target the current domain. If you would like to specify a new domain you can do so by setting the host property on the adapter.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  host: 'https://api.example.com'
});

Requests for person would now target https://api.example.com/people/1.

Path Customization

By default the JSONAPIAdapter will attempt to pluralize and dasherize the model name to generate the path name. If this convention does not conform to your backend you can override the pathForType method.

For example, if you did not want to pluralize model names and needed underscore_case instead of camelCase you could override the pathForType method like this:

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  pathForType: function(type) {
    return Ember.String.underscore(type);
  }
});

Requests for person would now target /person/1. Requests for user-profile would now target /user_profile/1.

Headers customization

Some APIs require HTTP headers, e.g. to provide an API key. Arbitrary headers can be set as key/value pairs on the JSONAPIAdapter's headers object and Ember Data will send them along with each ajax request.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  headers: {
    'API_KEY': 'secret key',
    'ANOTHER_HEADER': 'Some header value'
  }
});

headers can also be used as a computed property to support dynamic headers. In the example below, the headers are generated with a computed property dependent on the session service.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  session: Ember.inject.service('session'),
  headers: Ember.computed('session.authToken', function() {
    return {
      'API_KEY': this.get('session.authToken'),
      'ANOTHER_HEADER': 'Some header value'
    };
  })
});

In some cases, your dynamic headers may require data from some object outside of Ember's observer system (for example document.cookie). You can use the volatile function to set the property into a non-cached mode causing the headers to be recomputed with every request.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  headers: Ember.computed(function() {
    return {
      'API_KEY': Ember.get(document.cookie.match(/apiKey\=([^;]*)/), '1'),
      'ANOTHER_HEADER': 'Some header value'
    };
  }).volatile()
});

Authoring Adapters

The defaultSerializer property can be used to specify the serializer that will be used by this adapter. This is only used when a model specific serializer or serializer:application are not defined.

In an application, it is often easier to specify an serializer:application. However, if you are the author of a community adapter it is important to remember to set this property to ensure Ember does the right thing in the case a user of your adapter does not specify an serializer:application.

import DS from 'ember-data';

export default DS.JSONAPIAdapter.extend({
  defaultSerializer: '-default'
});

Community Adapters

If none of the built-in Ember Data Adapters work for your backend, be sure to check out some of the community maintained Ember Data Adapters. Some good places to look for Ember Data Adapters include:

• Ember Observer
• GitHub
• Bower