Object question

iges

Hi,

I've a question about objects, to explain it better an example:

A class named Car has an aggregation relation with a general class Parts. So in code the Car class contains a collection (array) of Parts.

Now the Parts class is used to derive more specific parts like Body, Engine and so on.

Now I would like to implement a method CreatePart (pName) in the Car class.

Question: Is there way in PHP to specify the exact class, meaning that the CreatePart should create specific part (Body, Engine) and not general Part.

What would be the best way to do this?

Regards,
iges.

olaf

Use a database!

OhLordy

Could you not have a switch in your constructor and pass an extra variable saying which class is to be called?

ahundiak

$pname = 'Engine';
$part =& new $pname;

Should do the trick.

iges

Hi,

this indeed does the trick, and the method will be short, just love it 😉. Big thanks, also to everyone else who gave their ideas.

I also made an example code:

<?php

// +---------------------------------------------------------------------------------
// Class definitions
// +---------------------------------------------------------------------------------
class Car {
	var $Parts;
	var $part_idx;

	function Car() {
		print "Building a car ;)<br>";
		$this->Parts = array();
		$this->part_idx = -1;
	}

	function AddPart($pPart) {
		$part = & new $pPart;
		$this->part_idx += 1;
		$this->Parts[$this->part_idx] = $part;
	}

	function PrintPartList() {
		$max = count($this->Parts);

		print "<br><u>Part List</u><br>";
		for ($i = 0; $i < $max; $i++) {
			$part = $this->Parts[$i];
			print $part->name."<br>";
		}
	}

}
// +---------------------------------------------------------------------------------
class Part {
	var $name;

	function Part () {
		$this->name = "General Part";
		print "Part init";
	}

}
// +---------------------------------------------------------------------------------
class Body extends Part {

	function Body () {
		parent::Part();
		$this->name = "Body";
		print " - Body<br>";
	}

}
// +---------------------------------------------------------------------------------
class Engine extends Part {

	function Engine () {
		parent::Part();
		$this->name = "Engine";
		print " - Engine<br>";
	}

}

// +---------------------------------------------------------------------------------
// Test code
// +---------------------------------------------------------------------------------

$newcar = new Car();

$newcar->AddPart("Body");
$newcar->AddPart("Engine");

$newcar->PrintPartList();
?>

iges

Oops, the image ref in php code is not from me ...