How do you create a custom adapter for ember.js?

For Ember Data

This is up to date as of Ember Data 1.0 beta 9.

Extend one of the Ember Data Adapters. To make it site wide:

App.ApplicationAdapter = DS.RESTAdapter.extend(....

To make it model specific:

App.FooAdapter = DS.RESTAdapter.extend(...

Then you will define the implementation you’d like to override. You always have the option to call this._super and revert to the base implementation. e.g.

App.NotesAdapter = DS.RESTAdapter.extend({
  find: function(store, type, id) {
    id = "foo" + id;
    return this._super(store, type, id);
  }
});

Or you can completely override the implementation:

App.NotesAdapter = DS.RESTAdapter.extend({
  find: function(store, type, id) {
    // Do your thing here
    return this.ajax(this.buildURL(type.typeKey, id), 'GET');
  },

  findAll: function(store, type, sinceToken) {
    // Do your thing here
    var query;

    if (sinceToken) {
      query = { since: sinceToken };
    }

    return this.ajax(this.buildURL(type.typeKey), 'GET', { data: query });
  },

  findQuery: function(store, type, query) {
    // Do your thing here
    return this.ajax(this.buildURL(type.typeKey), 'GET', { data: query });
  },

  findMany: function(store, type, ids, owner) {
    return this.ajax(this.buildURL(type.typeKey), 'GET', { data: { ids: ids } });
  },
   .....
});

To see the complete api you can override see: http://emberjs.com/api/data/classes/DS.RESTAdapter.html

Serializer

Often more important will be rolling your own serializer for massaging the data to fit your rest endpoint. Here’s some useful information from the transition document https://github.com/emberjs/data/blob/master/TRANSITION.md .

The short version is that once an Ajax request has completed, the resulting payload is sent through the following hooks:

1. The payload is sent to extractSingle if the original request was for a single record (like find/save) or extractArray if the original request was for an Array of records (like findAll/findQuery)
2. The default behavior of those methods is to pull apart the top-level of the payload into multiple smaller records.
3. Each of those smaller records is sent to normalize, which can do normalization a record at a time.
4. Finally, specific types of records can be specially normalized.

    App.PostSerializer = DS.RESTSerializer.extend({
      extractSingle: function(store, type, payload, id) {
        // massage
        this._super(store, type, payload, id);
      },
      extractArray: function(store, type, payload) {
        // massage
        this._super(store, type, payload);
      },
      normalize: function(type, hash, property) {
        // massage
        this._super(type, hash, property);
      }
    });

• use extractSingle and extractArray when the top-level of your payload is organized differently than Ember Data expects
• use normalize to normalize sub-hashes if all sub-hashes in the payload can be normalized in the same way.
• use normalizeHash to normalize specific sub-hashes.
• make sure to call super if you override extractSingle, extractArray or normalize so the rest of the chain will get called.

Rolling your own

App.FooAdapter = Ember.Object.extend({
  find: function(id){
    return $.getJSON('http://www.foolandia.com/foooo/' + id);
  }
});

Then from your route, or wherever

App.FooRoute = Ember.Route.extend({
  model: function(){
    var adapter = App.FooAdapter.create();
    return adapter.find(1);
  }
});

Now personally I’d inject the adapter onto the routes just to make my life easier:

App.initializer({
    name: "fooAdapter",

    initialize: function (container, application) {
        application.register("my:manager", application.FooAdapter);
        application.inject("controller", "fooAdapter", "my:manager");
        application.inject("route", "fooAdapter", "my:manager");
    }
});

Then on the route you could be lazier and do:

App.FooRoute = Ember.Route.extend({
  model: function(){
    return this.fooAdapter.find(1);
  }
});

Example: http://emberjs.jsbin.com/OxIDiVU/676/edit

You can read more about Ember without Ember Data: Ember without Ember Data