Here is what I came up with - it's one way to have polymorphic
capabilities in your components.
You define your component as an abstract class with abstract
functions, and thereafter, except for a single call before you use the
component the first time, it behaves exactly as a regular component
would, but you gain polymorphism.
In AppController:
============
//
// Imports, instantiates and stores an implementation instance of
// an abstract class just as cake would with a regular component.
// Enables abstract class components which need to be instantiated
only after
// the desired implementation is known.
//
function abstractComponent($componentName, $implementationType,
$import = true) {
if ($import) {
App::import('Component',$componentName);
}
$this -> $componentName =
call_user_func($componentName.'Component::getInstance',
$implementationType);
$this -> $componentName -> Startup($this);
}
In your controller:
=============
//
// Note: do not put the component in your $components class variable.
If you do, cake will try and instantiate
// it, but it will fail, because an abstract class cannot be
instantiated.
// You have to call the abstractComponent() function to do that.
//
function index() {
$this->abstractComponent('Reservation', HOTELS);
debug("Calling ReservationHotels: ".$this-
>Reservation-
>getPrice());
$this->abstractComponent('Reservation', CARS,
false);
debug("Calling ReservationCars: ".$this->Reservation-
>getPrice());
}
The Component containing the abstract class:
=================================
<?php
//
// General Reservation component -
// Abstract class with subclassed implementations
// for each reservation type.
//
abstract class ReservationComponent extends Object
{
var $controller;
var $name = 'Reservation';
function startup(& $controller) {
$this->controller = $controller;
}
//
// instantiate the appropriate implementation subclass and
// store it as the Reservation component.
//
static function getInstance($reservationType) {
switch ($reservationType) {
case HOTELS:
App::import('Component','ReservationHotels');
return new
ReservationHotelsComponent();
case CARS:
App::import('Component','ReservationCars');
return new ReservationCarsComponent();
default:
return false;
}
}
// Abstract functions...
abstract function getPrice();
}
?>
Example of a subclassed implementation:
==============================
<?php
//
// Subclassed implementation of ReservationComponent for hotels.
//
class ReservationHotelsComponent extends ReservationComponent
{
var $controller;
var $name='ReservationHotels';
function startup(& $controller) {
parent::startup($controller);
}
//
// Override the parent abstract functions.
//
function getPrice() {
return $this->name;
}
}
?>
The component files would be:
======================
reservation.php - the abstract class.
reservation_hotels.php - the hotels implementation subclass
reservation_cars.php - the cars implementation subclass
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