_MAJOR_ bug in OO-engine?

Anon

This is something that I couldn't get working in PHP 4.0.2:

I have a superclass which has a constructor and a variable.
The constructor takes one argument, any object inherited from itself.
Like so:

class Component {
var $childCount;
var $children;
function Component($owner) {
if ($owner != FALSE)
$owner->addChild($this);
}

function addChild($child) {
$this->children[$childCount] = $child;
echo "You have ".sizeof($this->children)." children!<br>";
$this->childCount++;
}

function showChildren() {
echo "You ended up with ".sizeof($this->children)." children!<br>";
}
}

I extend this class and execute the following:
$mother = new Component(FALSE);
$daughter = new Component($mother);
$mother->showChildren();

Was someone besides me expecting this:
You have 1 children!
You ended up with 1 children!
????
BUT!!!
You end up with 0 children!
If this is a bug it needs to be fixed FAST since this is very basic OO functionality. If this is non-working we have to switch to JSP and we don't want to do that!

Anon

HMMMM is it because you are passing mother by val instead of passing by ref? Try passing
mother by ref and I bet it will work.

Anon

Passing by reference, as Cliff suggested, may solve your problem, but I would rewrite the class in any case.

A constructor should create a new instance, maybe initialize some class variables, but that's about all. It shouldn't be modifying arguments unless that's absolutely necessary.

Why not have the constructor add a child instead of a parent? Then your final code would look like this:

          $daughter = new Component(FALSE);			$mother = new Component($daughter); 

          $mother->showChildren();

Or better yet, take the addChild function out of the constructor altogether, so that you have this:

          $daughter = new Component();			$mother = new Component(); 
$mother->addChild($daughter); 

          $mother->showChildren();

This requires you to type an extra line, but it makes your code much clearer. Months from now, when you're looking over this code, you won't have to refer back to the class to learn the relationship between $mother and $daughter.

Hope this helps,
Beth

Anon

First of all, Beth J: No, I do not agree with you. The constructor should take the owner if the owner is mandatory (which it is in this case). OO design should be intuitive and it shouldn't leave any room for errors. Forgetting to call "addChild" would be disastrous in this case, thus making it a mandatory, constructor argument.

Back to the problem... I've done it the way you want it.
Well. Here it is, I can use by reference, but the wierd thing is I can only do it once.
If I do it like this:
$papa = new Human();
$son = new Human();
$papa->addChild($son);
$grandson = new Human();
$son->addChild($grandson);
$papa->showAllChildren();

The method "showAllChildren()" itterates $papas' children
and recursevly itterates over the childrens children as well.
$papa has one child and calls $child->showAllChildren on that child. The child (should be $son in this example) however has ZERO children.

Why, I can't tell ya. The "addChild()" method has the argument set by reference and it stores the reference in an array. That array has one element in the "addChild()" method, but zero in all other methods.

Seems like there is still some "reference/value" problem.
But I have no idea where. I've designed thousands of applications using way more complex OO than this using C++ and Java, these things are very basic.

Anon

I conducted some more tests and the only conclusion I could come up with is that an array element cannot hold a reference to an object.
Since all my children are stored in a big array and they MUST be references (since changes can occur to the children after beeing added to the parents array) the array is useless to me.

Here's the test I performed:
$myObj = "Mama";
$array[0] = &$myObj;
$myObj .= " and Papa";
echo $array[0];

Out comes "Mama".

Is there a way to make a workaround on this one?
Or did I just mess up the reference here?

Anon

http://www.zend.com/codex.php?id=230&single=1

Check out this url on zend it has a object that does essentially what you are talking about also. I know that it works since I used it last night in a project.

Anon

What version of PHP are you running? I've got 4.0.2 and when I ran your code, it came out fine (echoed "Mama and Papa").

Beth