Resolve php endless recursion issue

Question

Hey all,

I'm currently running into an endless recursion situation.

I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern..

Here's whats going on:

Dispatcher.php

class Dispatcher {
...
    public function message($name, $method) {

    // Find the object based on the name
    $object = $this->findObjectByName($name);

    if(!$object->decorations))
            // Decorate the object
        $object = new $name($object); // This is where it locks up.
            $object->decorations = true;
    }

    return $object->$method();
...
}

class A {
    function __construct()
    {
        $Dispatcher->message("B", "getName");
    }

    public function getName() {
        return "Class A";
    }

}

class B {
    function __construct()
    {
            // Assume $Dispatcher is the classes
        $Dispatcher->message("A", "getName");
    }

    public function getName() {
        return "Class B";
    }

}

It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized.

I'm looking for some kind of queue implementation that will make messages wait for each other.. One where the return values still get set. I'm looking to have as little boilerplate code in class A and class B as possible

EDIT: I'm getting a lot of talk about the not_initialized method, unfortunately I feel that the discussion is going in the wrong direction. That's my fault, I'll explain the situation a little more (and better I hope). $object implements a decorator pattern - that is $object gets more features (methods) when I initialize class A and class B. I need to use those features made available from the decorations in the messaging method, that's why if its not yet decorated, decorate it. I really do not think not_initialized would have been the issue because when say $objectA is checked it is not yet decorated - So I want to add those methods to it. Class A and B are decorator classes. So not_initialized is correct at the time. It gets stuck when I try to decorate the object. I changed the code to better reflect this situation.

Any help would be immensely helpful..

Thanks! Matt Mueller

Answer 1

This is not an example of deadlock, but of endless recursion. Most likely your not_initialized function returns true until the constructor has been fully run. As a result, constructing an object of type A will indirectly call the B constructor, which will call the A constructor, ad infinitum.

You will have to change the not_initialized function, or move the message dispatching out of the constructors if you can.

Deadlock is a situation that involves multiple processes. In this case, there is only a single process.