Creating Listeners

Key to understanding Mach-II is discovering how to access variables passed in an event. For Fusebox developers the technique will feel similar to referencing form variables in the attributes scope: the framework does the conversion of form and url variables to properties of a Mach-II event (Event).

In our demo we post a form and process the variables with a Mach-II listener class. This class is a regular PHP class that extends MachII.framework.Listener:

class phpMachII_model_processForm extends MachII_framework_Listener
{
 function configure() {} // Called automatically by framework
}

Figure 9  ./model/processForm.php ~ A listener class

These variables are accessed by the listener class by calling Event like this:

$event->getArg(‘username’);

Figure 10  Accessing a value in Event

Listener classes are called by the framework using the mappings defined in the type attribute of a <listener> node (fig. 8). A method is defined in the event handler and then passed to the listener. Mach-II locates the listener class in its directory and calls the desired method. Finally, the listener receives the Event object and processes the request.

class phpMachII_model_processForm extends MachII_framework_Listener
{
 // Called automatically
 function configure() {}
 
 function validateForm($event) {
 
  // Retrieves values posted in form
  $thisUN = $event->getArg('username');
  $thisPW = $event->getArg('password');
 
  if (isset($thisUN) && isset($thisPW) && $thisUN == "admin" && $thisPW == "machii") {
   $message = "Success";
   $this->announceEvent('success', $message);
  } else {   
   $message = "Failure";
   $this->announceEvent('noSuccess', $message);
  }
 
  return $message;
 }
 
}

Figure 11  ./model/processForm.php ~ accessing form variables from a listener by executing Event’s getArg method.