Criando uma API REST com CakePHP

json.ctp

<?php echo json_encode($data); ?>

RestController.php

<?php
/**
 * Created by PhpStorm.
 * User: sergiovilar
 * Date: 05/04/14
 * Time: 11:44 PM
 */

class RestController extends AppController{

    public function index($id = null) {

        switch($this->request->method()){

            case 'GET':

                if(!empty($id)){
                    $this->view($id);
                }else{
                    $this->listAll();
                }

                break;

            case 'POST':

                if(!empty($id)){
                    $this->add();
                }else{
                    $this->update($id);
                }

                break;

            case 'PUT':

                $this->update($id);

            break;

            case 'DELETE':

                $this->delete($id);

            break;



        }


    }

    // Métodos privados

    private function renderJSON(){

        $this->layout = null;
        $this->set('data', array('result' => $this->out));
        $this->render('/Elements/json');

    }

    private function returnError($error){

        $this->layout = null;
        $this->set('data', array('error' => $error));
        $this->render('/Elements/json');

    }

    private function returnSuccess($msg){

        $this->layout = null;
        $this->set('data', array('success' => $msg));
        $this->render('/Elements/json');

    }

    protected function listAll(){

        $this->out = $this->{$this->model}->find('all');
        $this->renderJSON();

    }

    private function view($id){

        $this->out = $this->{$this->model}->findById($id);
        $this->renderJSON();

    }

    protected function add() {

        $this->{$this->model}->create();

        if ($this->{$this->model}->save($this->request->data)) {
            $this->returnSuccess("Registro adicionado com sucesso");
        } else {
            $this->returnError("Houve um problema ao adicionar o registro");
        }

    }

    protected function update($id) {

        $this->{$this->model}->id = $id;

        if ($this->{$this->model}->save($this->request->data)) {
            $this->returnSuccess("Registro atualizado com sucesso");
        } else {
            $this->returnError("Houve um problema ao atualizar o registro");
        }

    }

    protected  function delete($id) {

        if ($this->{$this->model}->delete($id)) {
            $this->returnSuccess("Registro excluído com sucesso");
        } else {
            $this->returnError("Houve um problema ao excluir o registro");
        }

    }

} 

SampleController.php

<?php
App::uses('AppController', 'Controller');

require_once(ROOT . DS . 'app' . DS . 'Controller' . DS . 'RestController.php');

/**
 * Sample Controller
 *
 */
class SampleController extends RestController {

    public $model = 'Sample';

}