With the help of this and this I made a plugin to add a custom fields to the article component. It works fine but I would like to make these custom fields mandatory and only for a specific article category.

The plugin is called "acf"

acf.php :

 defined ( '_JEXEC' ) or die ( 'Restricted access' );
 class plgContentAcf extends JPlugin {
    protected $autoloadLanguage = true;
    function onContentPrepareForm($form, $data) {
        $app = JFactory::getApplication();
        $option = $app->input->get('option');
        switch($option) {
            case 'com_content':
                if ($app->isAdmin()) {
                    JForm::addFormPath(__DIR__ . '/forms');
                    $form->loadFile('content', false);
                return true;
        return true;

acf.xml :

<?xml version="1.0" encoding="utf-8"?>
<extension version="3.4" type="plugin" group="content" method="upgrade">
    <description>This is the description of the plugin</description>
        <filename plugin="acf">acf.php</filename>
        <language tag="en-GB">en-GB.plg_content_acf.ini</language>
        <language tag="en-GB">en-GB.plg_content_acf.sys.ini</language>


<?xml version="1.0" encoding="UTF-8"?>
  <fields name="attribs" >
    <fieldset name="acf" >
        description="Description here"
  • What about adding a category selector as a plugin parameter in your XML file? – Lodder Mar 21 '16 at 9:26
  • @Lodder that would be great, how should I do that (I edited the acf.xml file in the question)? – web-tiki Mar 21 '16 at 9:30
  • 2
    I'm just mocking up and code and testing. One question though....you want this to only appear on articles that are assigned to a specific category, but what if you're creating a new article. You first have to assign the category, save it, then the custom form fields will appear, then you need to save again. – Lodder Mar 21 '16 at 9:45
  • thx @Lodder good question. What if the custom field would alway render, and be hidden/shown as the category is selected with JS. Then the only issue would be to allow other categories to be saved without the mandatory custom field. Is that possible? – web-tiki Mar 21 '16 at 9:52

Right, been playing around and got it working.

You're firstly going to need to add the parameter to select a category to your acf.xml file, like so:

    <fields name="params">
        <fieldset name="basic">
            <field name="category" type="category" extension="com_content" label="Select a category" />

Then in your acf.php:

class plgContentAcf extends JPlugin 
    protected $autoloadLanguage = true;

    function onContentPrepareForm($form, $data)
        $app = JFactory::getApplication();

        if ($app->isAdmin())
            $option = $app->input->get('option');
            $view   = $app->input->get('view');

            if ($option === 'com_content' && $view === 'article')
                $model = JModelLegacy::getInstance('Article', 'ContentModel');
                $catid = $model->getItem($app->input->get('id'))->catid;

                if ($this->params->get('category') === $catid)
                    JForm::addFormPath(__DIR__ . '/forms');
                    $form->loadFile('content', false);

            return true;

As you can see, I've made a few changes to the code, such as:

  • Remove the switch/case.
  • Ensure all code is only executed when isAdmin is true
  • Ensure the form field and params are retrieved only on the article view in the com_content component

The form is then only loaded when the ID of the category selected in the plugin options, match the category ID of the current article.

Hope this helps

| improve this answer | |
  • This works like a charm and will get me going. Thx a lot – web-tiki Mar 21 '16 at 10:43
  • 1
    Nice job guys... Can you find a way to share installable package with the rest of us, by any chance? ;-) – Mikan Mar 21 '16 at 10:49
  • @Mikan, I wont do that cause it's not my extension to make available. If the OP wants to, I think Github would be a good place to put it ;) – Lodder Mar 21 '16 at 10:56
  • @Lodder - Agreed, on both counts... :-) – Mikan Mar 21 '16 at 11:00
  • @web-tiki - You can do if you like :) – Lodder Mar 21 '16 at 11:13

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