How stop update/installation by install script and mantain actual folder?

Question

I found by Joomla 3.x, that I can use an install script something like this:

class lib_exampleInstallerScript
{
    public function install($adapter) 
    {
        // during install
    }

    public function uninstall($adapter) 
    {
        // during uninstall
    }

    public function update($adapter) 
    {
        // during update
    }

    public function preflight($route, $adapter) 
    {
        // before all
    }

    public function postflight($route, $adapter) 
    {
        // after all
    }
}

I was trying to create a script that verifies if the current extensions to be installed have higher version than the installed on system. Something like this:

public function preflight($type, $parent){

    // Return true if version to be installed is higher
    if (!$this->isHigherVersion($parent)){
        $msg = "<p>Error msg.</p>";
        JLog::add($msg, JLog::WARNING, 'jerror');
        return false;
    }
}

However, it seems that before getting into the preflight, joomla deletes the contents of the folder in the installed extension, and as I stop the process in the preflight, I get a folder without the files, just the installation script. This shoul work when extension will installed or updated.

Answer 1

To get the current version, you need to get the vesion from the #__extensions table and compare them. This is the script I wrote for my extensions...I've dded some comments in there to help you:

class lib_exampleInstallerScript
{
    protected $release = '';

    protected $extension = 'lib_mylibrary';

    public function preflight($type, $parent)
    {
        // Module manifest file version
        $this->release = $parent->get('manifest')->version;

        // Abort if the module being installed is not newer than the currently installed version
        if (strtolower($type) === 'update')
        {
            $manifest   = $this->getItemArray(JFactory::getDbo()->quote($this->extension));
            $oldRelease = $manifest['version'];

            // Someone is trying to install a lower version than is currently installed
            if (version_compare($this->release, $oldRelease, '<'))
            {
                // Throw some error message and return false
                JApplicationCms::getInstance('site')->enqueueMessage('Error msg'), 'error');

                return false;
            }

            // The version being installed is higher than what is currently installed
            if (version_compare($oldRelease, $this->release, '<'))
            {
                // You can execute a function here

                // If you want to compare a specific version.
                if (version_compare($oldRelease, '2.0.0', '<='))
                {
                    // Update function for version 2.0.0
                    // $this->updateToVersionTwo();
                }
            }
        }
    }

    protected function getItemArray($identifier)
    {
        $db = JFactory::getDbo();

        $query = $db->getQuery(true)
            ->select($db->qn('manifest_cache'))
            ->from($db->qn('#__extensions'))
            ->where($db->qn('element') . ' = ' . $identifier);
        $db->setQuery($query);

        // Load the single cell and json_decode data
        $array = json_decode($db->loadResult(), true);

        return $array;
    }
}

Hope this helps