Including modifiers when extending nodes

ATK Howto: Including modifiers when extending nodes Complexity: advanced Author: June Henriksen <juneih@linpro.no>

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Intro

ATK features a concept called 'modifiers' that allows one to change functionality of a node without touching the original code of the node (See the 'Using modifiers' howto).

The way modifiers work however, prevents modifiers from being applied to classes that extend the node. This may be fixed in a later version of ATK. For now, you can use this howto which presents a workaround to this problem.

Adding modifiers to derived nodes

All modifiers added to a node run from the node's init function. Which modifiers that runs however, depends on the m_type of a node. When you extend a node, you get a new m_type if you set the atkNode in the constructor.

$this->atkNode("nodename");

In order to have the modifiers run, some changes has to be made in the extended node's init node.

The following is an example init_node for a node that extends the timereg.hours node:

  function init()
  {
    $ret = parent::init();
    $oldtype = $this->m_type;
    $oldmodule= $this->m_module;
    $this->m_type='hours';
    $this->m_module='timereg';
  
    global $g_modifiers;
  
    if (isset($g_modifiers[$this->atknodetype()]))
    {
      foreach ($g_modifiers[$this->atknodetype()] as $modulename)
      {
        $module = &getModule($modulename);
        $module->modifier($this);
      }
    }
    $this->m_module=$oldmodule;
    $this->m_type = $oldtype;
  
    return $ret;
  }

As mentioned, this example is for running the modifiers added to the hours node, but this can of course be exchanged for any other node. In fact, the only thing that needs to be changed in this code is the nodename ('hours') and modulename ('timereg')! Remember, the function itself is put in the extending node.

The result of including this is that you now will have access to all the attributes added by modifiers to the node that is extended.

--juneih 16:29, 23 November 2006 (CEST)