How can I display contents of all instances of an object?

Corey_M

I have a class named "car" which contains a handful of simple member variables such as "color" and "year" .. and I've created a bunch of instances of it with various names such as "mercedes" and "ferrari" -- how can I quickly/easily display all instances and their respective values as seen below?

mercedes
gold
1964

ferrari
red
1969

Thanks for any help. 🙂

laserlight

What is your current car class? (As in its member functions and member variables.)

Corey_M

Shouldn't matter, should it?

But let's say then for the class

class car {

// member variables
var $model;
var $color;
var $price;
var $year;

// member functions
function setModel($var) {
    $this->model=$var;        
}
function getModel () {
    echo $this->model;  
}
function setColor($var) {
    $this->color=$var;        
}
function getColor () {
    echo $this->color;  
}
function setPrice ($var) {
    $this->price=$var;        
}
function getPrice () {
    echo $this->price;  
}
function setYear($var) {
    $this->year=$var;        
}
function getYear () {
    echo $this->year;  
}

}

And then let's say there are half a dozen instances of this class. How can I display all the instances and their contents without knowing how many there are, or anything but the class name?

Thank you.

NogDog

If this is a necessary part of your application, I'd suggest creating something in the way of a registry class/object in which you can keep track of the objects of interest. If just for debugging or such, perhaps you could use the [man]get_defined_vars[/man] function, something like:

$vars = get_defined_vars();
foreach($vars as $var)
{
   if(is_a($var, 'car'))
   {
      printf(
         "<ul><li>&#37;s</li>\n<li>%04d</li>\n<li>%s</li></ul>\n", 
         $var->model, 
         $var->year, 
         $var->color
      );
   }
}

Corey_M

I'd suggest creating something in the way of a registry class/object in which you can keep track of the objects of interest

Surely there must be a simple way to quantify objects.

NogDog

It doesn't have to be all that complicated. At its simplest it might be something like:

class CarCollection
{
   private $cars = array();

   public function addCar(Car $car)
   {
      $cars[] = $car;
   }

   public function getCars()
   {
      return $this->cars;
   }
}

Then you could use it as:

$collection = new CarCollection();

$car1 = new Car();
$collection->addCar($car1);
$car1->setColor('Blue'); // and so forth...

$car2 = new Car();
$collection->addCar($car2);
$car2->setColor('Red'); // and so forth...

foreach($collection->getCars() as $car)
{
   echo "<p>Color: " . $car->color . " and so forth...</p>\n";
}

Corey_M

Why can't I just enumerate my existing class?

NogDog

Corey_M;10894374 wrote:
Why can't I just enumerate my existing class?

I'm afraid I don't know what that means.

Corey_M

I'm afraid I don't know what that means.

Surely there must be a way to "get all objects" instantiated from the original class?

laserlight

Corey_M wrote:
Surely there must be a way to "get all objects" instantiated from the original class?

I do not think so, but you can write the class such that it keeps track of its instances, much like how a singleton keeps track of its single instance. One of the ideas is to have a static member variable that is an array of the class instances, and to only allow instances to be created via a static member function that updates this static member variable (i.e., you declare the constructor to be private).

However, do you really need to "display all the instances and their contents without knowing how many there are, or anything but the class name"?

EDIT:
By the way, you might not need a static member function to create objects. The constructor could be made public and yet add the new object ($this) to the static member array.