Plugins

The Solution:

Couldn't you save the values somewhere else, for example in a custom-table? You could read that value on every OnDocFormSave, increment it, save the incremented value back to your custom-table and to your TV at the same time.

This way the value would really increment on each save.

Here is my complete procedure to achieve my version system:

Step 1: Create a new table in the MODX database called "modx_site_content_version" with three columns "id", "contentid" and "version" (set "id" column as INDEX):

CREATE TABLE `modx_site_content_version` (
  `id` int(11) NOT NULL,
  `contentid` int(11) NOT NULL,
  `version` int(11) NOT NULL
) DEFAULT CHARSET=utf8;
ALTER TABLE `modx_site_content_version` ADD PRIMARY KEY(`id`);
ALTER TABLE `modx_site_content_version` CHANGE `id` `id` INT(11) NOT NULL AUTO_INCREMENT;
ALTER TABLE `modx_site_content_version` ADD INDEX(`id`);

Step 2: Create a new snippet called "createXpdoClasses" and fill it with the code available at Bob's Guides, thanks to Bob!

Step 3: Create a new resource called "createXpdoClasses" with no richtext editor and put this code in it:

[[!CreateXpdoClasses? &myPackage=`Version` &myPrefix=`modx_site_content_`]]

-> View the resource one time in your browser.

-> Delete your "createXpdoClasses" resources and snippet. We do not need them anymore.

Step 4: Create a new plugin called "version" on the "onDocFormSave" event. This will increment the version.

addPackage('Version', $path . 'model/','modx_site_content_');
$currentResource= $modx->getObject('Version', array('contentid' => $id));
     
if (empty($currentResource)) {
    $newResource = $modx->newObject('Version', array(
        'contentid' => $id,
        'version' => 1
    ));
    $newResource->save();
}
else {
    $currentResource->set('version', $currentResource->get('version') + 1);
    $currentResource->save();
}
 
unset($path, $result, $currentResource, $newResource, $id);

Step 5: To get the version on templates and chunks, we will use this little snippet called "getVersion":

<?php
$result = $modx->query("SELECT version FROM modx_site_content_version WHERE contentid=$id");
$row = $result->fetch(PDO::FETCH_ASSOC);
return $row['version'];
unset($result, $row);

We use it this way in templates:

[[getVersion?id=`[[*id]]`]]

Step 6: To generate the version on all existing resources, simply create and run a new snippet "versionAllResources":

<?php
$resources = $modx->getCollection('modResource', array('class_key'=>'modDocument'));
  
foreach ($resources as $resource) {
    $path = MODX_CORE_PATH . 'components/version/';
    $result = $modx->addPackage('Version', $path . 'model/','modx_site_content_');
    $currentResource= $modx->getObject('Version', array('contentid' => $resource->get('id')));
     
    if (empty($currentResource)) {
        $newResource = $modx->newObject('Version', array(
            'contentid' => $resource->get('id'),
            'version' => 1
        ));
        $newResource->save();
    }
    else {
        $currentResource->set('version', $currentResource->get('version') + 1);
        $currentResource->save();
    }
}