apiPathFor

adapter.js

import DS from 'ember-data';

export default DS.ActiveModelAdapter.extend({
 
  host: 'http://customhost.dev',
  namespace: 'api/v1'

});

api-path-for.js

DS.Store.reopen({

  apiPathFor: function() {
    var url = arguments.length ? Array.prototype.slice.call(arguments).join('/') : ''
      , adapter = this.adapterFor('application')

    return [adapter.urlPrefix(), url].join('/');
  }

});

Use case inside a route (or object with access to DS.Store):

actions: {

  doSomething: function() {
    var param1 = 1;
    var param2 = 'test'
    var url = this.store.apiPathFor('custom/thing', param1, param2);

    // http://customhost.dev/api/v1/custom/thing/1/test
    console.log(url);
  }

}

Ah, shit. https://github.com/emberjs/data/blob/v1.0.0-beta.12/packages/ember-data/lib/adapters/rest_adapter.js#L552