Adding category parameter(s) - joomla

Question

I'm developing extension, using native Joomla categories. I would like to add one additional parameter in category editor, which only be used when editing my extension's category.
The question:
Is it possible without overriding Joomla core files?

Answer 1

The previous answer (new XML file) is very close, but doesn't quite work in Joomla 3.x. To make it work I had to change the name attribute of the fields element to "params" as follows:
<?xml version="1.0" encoding="utf-8"?>
<form>
<fields name="params">
<fieldset name="basic" label="Group settings">
<field name="group_id" type="list" default="" label="Select group:">
<option value=""></option>
<option value="1">Group 1</option>
<option value="2">Group 2</option>
<option value="3">Group 3</option>
</field>
</fieldset>
</fields>
</form>
This way, the custom options show in the options tab of the category edit screen.
Also, if you have more than one type of category in your component (for example, "com_mycomponent.mycategorytype"), you need to make the name of the XML file "category.mytype.xml".

Answer 2

Well actually after night of no sleep i was able to find an elegant native solution.
Unfortunately Joomla devs didn't documented it, but it appears that in your extension you create file:
/administrator/components/com_YourName/models/forms/category.xml and add there a fieldset "attribs" it automatically appears in your extension's category manager.
Sample code of category.xml here:
<?xml version="1.0" encoding="utf-8"?>
<form>
<fields name="attribs">
<fieldset name="attribs" label="Group settings">
<field name="group_id" type="list" default="" label="Select group:">
<option value=""></option>
<option value="1">Group 1</option>
<option value="2">Group 2</option>
<option value="3">Group 3</option>
</field>
</fieldset>
</fields>
</form>

Answer 3

UPDATED
Yes, this can also be done without hacking core files.
You can create a template override for the administrator com_categories component.
Copy this file:
administrator/components/com_categories/views/category/tmpl/edit.php
in this path (you need to create the corresponding directories):
administrator/templates/bluestork/html/com_categories/category/edit.php
In this new file you can work all your magic.
If you need something more advanced, you can use a plugin that allows you to override models and any other part of the component: Plugin Override