Objects having knowledge of each other

Question

In Zend Framework ,Zend_Application object has a bootstrap object to bootstrap or configure the components.Bootstrap class in turn have access to zend_application object to access configuration parameters.
My Question is that what kind of pattern is this or is it a code smell because of circular dependency.

Answer 1

Zend Framework 1 is bloated, that's for sure.

The reason for that $_application property representing a bi-directional relation is due to the module's independent bootstrap files.

It's strange, I think, because when dealing with modules, instead of having the Zend_Aplication set you'll have the main bootstrap instead:

/**
 * Set application/parent bootstrap
 *
 * @param  Zend_Application|Zend_Application_Bootstrap_Bootstrapper $application
 * @return Zend_Application_Bootstrap_BootstrapAbstract
 */
public function setApplication($application)
{
    if (($application instanceof Zend_Application)
        || ($application instanceof Zend_Application_Bootstrap_Bootstrapper)
    ) {
        if ($application === $this) {
            throw new Zend_Application_Bootstrap_Exception('Cannot set application to same object; creates recursion');
        }
        $this->_application = $application;
    } else {
        throw new Zend_Application_Bootstrap_Exception('Invalid application provided to bootstrap constructor (received "' . get_class($application) . '" instance)');
    }
    return $this;
}

There's a lot of code smell too:

/**
 * Constructor
 *
 * Sets application object, initializes options, and prepares list of
 * initializer methods.
 *
 * @param  Zend_Application|Zend_Application_Bootstrap_Bootstrapper $application
 * @return void
 * @throws Zend_Application_Bootstrap_Exception When invalid application is provided
 */
public function __construct($application)
{
    $this->setApplication($application);
    $options = $application->getOptions();
    $this->setOptions($options);
}

The boostrap file need the options, so instead of asking for the options, it expects the Zend_Application to then get the options:

$options = $application->getOptions();
$this->setOptions($options);

It seems like they simply ignore the type of interface expected by the setApplication() method and it can be one of the followings:

• Zend_Application
• Zend_Application_Bootstrap_Bootstrapper
• Zend_Application_Bootstrap_ResourceBootstrapper

I would give up trying to understand this mess and switch to ZF 2, though ;)