K2:How to run a certain task every time an item is saved

Question

I am using k2 to buildg my Joomla 3.5 site. My k2 items are basically youtube videos, every youtube video has a URL pattern for its preview image and I want it to be the item's image. But I don't want to bother with the repetitive job (copying the video ID, fitting it into the URL, and saving it as the item's image) every time I create an item. So I am thinking maybe I can write some script to automatically get the images(it is easy to do once the video's id is provided). The problem is, this script has to be exectued every time I create an item.

I just start to learn some basic things about Joomla extension developing, my question is, which category does the thing I want to fall into? Shall it be a plugin? Or a k2 plugin? Or there is totally no interface for this kind of thing and I will have to hack some PHP file?

Furthermore, I also have some node.js script to scrape the description of the Youtube videos(Yes I am being lazy again, I don't want to copy and paste those descriptions every time I create an item). How do I get Joomla to run these node.js scripts?

Answer 1

You need a K2 plugin if you are not yet using K2 V3, otherwise a regular Joomla plugin, if I remember correctly.

Basic sceleton for what you need would be something like

<?php
defined('_JEXEC') or die ('Restricted access');

JLoader::register('K2Plugin', JPATH_ADMINISTRATOR . '/components/com_k2/lib/k2plugin.php');
JLoader::register('K2HelperUtilities', JPATH_COMPONENT . '/helpers/utilities.php');
JLoader::register('K2ModelItemlist', JPATH_COMPONENT . '/models/itemlist.php');
JTable::addIncludePath(JPATH_COMPONENT_ADMINISTRATOR . '/tables');

class plgK2Myplugin extends K2Plugin {

   //params needed for K2
   public $pluginName = 'myplugin';
   public $pluginNameHumanReadable = 'My plugin';

   public function __construct(&$subject, $params) {
      parent::__construct($subject, $params);
   }

   public function onAfterK2Save(&$item, $isNew) 
   {
       // this is where your logic goes
   }
}

Then you can edit the $item variable and change the image variable to what you want