Actions and Filters and Classes, Oh My!

Comments

1. Amaury (1 comments.) says:

   8/26/2009 at 6:21 pm

   You also can use
   array( &$this, ‘myFunction’ )

   into the class… and use a global var for initialize the class.
2. HG (2 comments.) says:

   8/26/2009 at 6:43 pm

   I was searching for that exact solution. Thank you for posting it.
3. Hikari (79 comments.) says:

   8/27/2009 at 1:05 am

   Is this $the_class_initiator_variable an object, or is it the class name?
   • James Dimick (23 comments.) says:

     8/27/2009 at 3:14 am

     It’s the variable that is used to initialize the class. Like:

     class myClass {
function the_function() {
echo 'whatever';
}
}

     $myVar = new myClass();

     remove_filter('wp_head', array(&$myVar, 'the_function'));

     Does that help?
     • Hikari (79 comments.) says:

       8/29/2009 at 11:06 am

       tnx for the explanation and the exemple guys!

       I’m starting in wordpress plugin development, and I’m having trouble using OOP with WP.

       What I’m currently doing is using a core file with the class and another file with hook functions and so on. I also didn’t know how to make an object global, I’ll try that and then adapt my plugins for it!

       BTW: I subscripted to this post comments feed but I’m receiving report of other posts comments too. I used the correct feed URL, there seems to be a bug here.
4. kovshenin (13 comments.) says:

   8/27/2009 at 3:14 am

   Hikari, it’s an object, therefore we can’t use &$this in this particular case. Since it’s cool to code plugins using the php OOP mode (i.e. using classes) then the actions and filters should probably be applied within the class, where you can actually use the array(&$this, ‘func_name’) that Amaury suggested above.

   The init section would be quite tricky in this case. Here’s a construction I like to use (suppose your class is called MyPlugin):

   add_action(“init”, “MyPlugin”); function MyPlugin() { global $MyPlugin; $MyPlugin = new MyPlugin(); }

   I don’t know who to thank but the first time I’ve seen this was in Viper007Bond’s Video Quicktags plugin.

   One more thing, a callback function is actually a php term, not wordpress. The wordpress codex says that the add_action, add_filter, and so on accept any valid callback functions. The php manual says that a callback function could be simply “my_func” or array(&scope, “my_func”). Thus, it works =)

   Cheers,
   ~ @kovshenin
   • James Dimick (23 comments.) says:

     8/27/2009 at 3:17 am

     Thanks for the response and thanks for clearing that up!
     • kovshenin (13 comments.) says:

       8/27/2009 at 3:21 am

       No problemo =) I actually just realized that you were refering to theme development as opposed to plugin development, where things are slightly different and perhaps a little bit more complex. I’m very used to add_action My apologies if I missed anything

       Have a great day!
   • Viper007Bond (91 comments.) says:

     8/27/2009 at 5:14 am

     The manual page he is referring to is this one BTW: http://www.php.net/call_user_func

     Also note that it’s important to wait until “init” to start your class. If you don’t, some functions (current_user_can()) for example will fail to work (or even be defined!).
     • kovshenin (13 comments.) says:

       8/27/2009 at 5:27 am

       Right, thank you Viper.

       What can you say about plugin activation and deactivation hooks? I believe they’re fired before the init level (I’m talking about the register_activation_hook function. The old way isn’t being used any longer AFAIK), therefore my plugin_activate and plugin_deactivate functions should be in the global scope and I can’t really wrap them up in my main plugin class unless I init it at an earlier level, which is pretty risky.
       • Viper007Bond (91 comments.) says:

         8/27/2009 at 5:29 am

         Honestly I’ve never dealt with them. Never had a need.
5. kovshenin (13 comments.) says:

   8/27/2009 at 3:18 am

   Ah, totally forgot.. Thank you James, for explaining this. Great post
   • James Dimick (23 comments.) says:

     8/27/2009 at 3:35 am

     It’s my first here on WLTC.
     Hopefully there will be much more to come.
     • Viper007Bond (91 comments.) says:

       8/27/2009 at 5:19 am

       It’s nice seeing some more technical posts on WTC, even if I already knew it.
6. Camilo (1 comments.) says:

   8/27/2009 at 9:08 pm

   Well, the problem is if you don’t have any access to that variable. If the plugin writer doesn’t make it a global accessible variable, there’s no easy way to retrieve that same variable, thus making it hard to remove the filter for a variable you don’t have any reference to.
   It’s very common for me to hook an object to WordPress inside a function and leave no other reference to that object.
   • Viper007Bond (91 comments.) says:

     8/28/2009 at 7:57 pm

     Then the plugin author is doing it wrong.