---------- Forwarded message ----------
From: Yeti <yeti@xxxxxxxxxx>
Date: Fri, Jul 11, 2008 at 2:08 PM
Subject: Re: Question regarding OO
To: Eric Butera <eric.butera@xxxxxxxxx>
I understand my error in thinking now.
Apple can't extend Tree.
Oak, Evergreen or Willow extend Tree.
I thank you all for helping me to understand.
On 7/11/08, Eric Butera <eric.butera@xxxxxxxxx> wrote:
>
> On Fri, Jul 11, 2008 at 12:03 PM, Yeti <yeti@xxxxxxxxxx> wrote:
> > <?php
> >
> > /*
> >
> > I have a question here regarding object orientation in PHP and any other
> > language.
> >
> > Let's start with some hypothetical code:
> >
> > */
> >
> > // <--- 1st CLASS
> >
> > class ParkingLot {
> >
> > var size; // size in sq feet
> >
> > var max_number_of_cars; // how many cars there is space for
> >
> > function __construct($size, $max_cars) {
> >
> > $this->size = $size; $this->max_number_of_cars = $max_cars;
> >
> > }
> >
> > };
> >
> > cpark = new ParkingLot(50000, 17);
> >
> > // <--- 2nd CLASS
> >
> > class ParkingSpace extends ParkingLot {
> >
> > var ps_ID; // ID of the parking space ( 1 .. max_number_of_cars )
> >
> > var occupied_by; // ID of the car on the parking space
> >
> > var st_time; // Unix time stamp set when the car parks
> >
> > function __construct($car, $id) {
> >
> > $this->st_time = time();
> >
> > $this->occupied_by = $car;
> >
> > $this->ps_ID = $id;
> >
> > }
> >
> > };
> >
> > /*
> >
> > OK, so i got a parking lot class and its subclass parking space.
> >
> > Now the question:
> >
> > I want a list of occupied parking spaces, where do I put that? One might put
> > it into the ParkingLot Class, but wouldn't that be a recursion (a child
> > instance in the parent class)?
> >
> > */
> >
> > $occ_parking_spaces = array();
> >
> > $occ_parking_spaces[] =& new ParkingSpace('Joes Car', 8);
> >
> > $occ_parking_spaces[] =& new ParkingSpace('My Prshe', 17);
> >
> > $occ_parking_spaces[] =& new ParkingSpace('Toms Caddy', 4);
> >
> > /*
> >
> > After a while a method to print all occupied spaces is necessary. Correct me
> > if I'm wrong, but I usually add it to the ParkingLot class.
> >
> > class ParkingLot {
> >
> > // previous code ...
> >
> > var $occ_parking_spaces = array();
> >
> > function print_occ_spaces() {
> >
> > var_dump($this->occ_parking_spaces)
> >
> > }
> >
> > };
> >
> > What bothers me here is that I'm actually having a list of child classes in
> > the parent class, is there a better/correct way to do this?
> >
> > I hope I made myself clear.
> >
> > Greetz,
> >
> > Yeti
> >
> > */
> >
> > ?>
> >
>
>
> Listen to what everyone else has said so far. Look up IS-A versus
> HAS-A. Favor composition over inheritance. You want your parking lot
> to have spaces, but spaces don't have to be in a parking lot.
>
> http://www.javacamp.org/moreclasses/oop/oop5.html
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