Component upgrade 2.5 to 3.0 getting error

Question

I am trying to upgrade a component from 2.5 to 3.x. But while doing so I am getting error from controller.php file. Error message is like the following: Fatal error: Call to a member function get() on a non-object in /home/abs/public_html/joomla34/administrator/components/com_refix/controller.php on line 20 Here is the code of controller.php file:

defined('_JEXEC') or die;

class PrefixController extends JControllerLegacy {
/**
 * constructor
 * 
 * @access public
 */
public function __construct() {

    require_once JPATH_COMPONENT . '/helpers/prefix.php';
    JFactory::getApplication()->input->get('view', $this->input->get('view', 'tableprefix'));
    parent::__construct();
    $view = $this->input->get('view');
    PrefixHelper::addSubMenu((isset($view)) ? $view : '');
}

/**
 * check new table prefix
 * 
 * @access private
 * @return boolean
 */
private function checkTablePrefix() {
    $new_prefix = $this->input->get('new_prefix');
    if(!preg_match('/^[a-zA-Z]+[a-zA-Z0-9_]*$/',$new_prefix)) {
        return false;
    } else {
        return true;
    }
}

/**
 * rename table prefix and update configuration.php file
 * 
 * @access public
 */
public function update() {
    $msg = '';
    if(!$this->checkTablePrefix()) {
        $msg = '<span class="prefix_error">' . JText::_('COM_PREFIX_PREFIX_NEW_PREFIX_DESC') . '</span>';
    } else {
        $model = $this->getModel('tableprefix');
        $new_prefix = $this->input->get('new_prefix');
        if($model->renamePrefix($new_prefix)) {
            $msg .= JText::_('COM_PREFIX_SUCCESS:TABLE_PREFIX_ALREADY_UPDATED');

            // update configuration file
            if($this->input->get("update_config") == '1') {
                // backup configuration file
                if($this->input->get("backup_before") == '1') {
                    $msg .= "<br />";
                    if($model->backupConfig()) {
                        $msg .= JText::_('COM_PREFIX_SUCCESS:BACKUP_THE_CONFIGURATION.PHP_FILE');
                    }  else {
                        $msg .= '<span class="prefix_error">' . JText::_('COM_PREFIX_ERROR:CONFIGURATION.PHP_FILE_COULD_NOT_BE_BACKUP') . '</span>';
                    }
                }

                $msg .= "<br />";
                if($model->editConfig($new_prefix)) {
                    $msg .= JText::_('COM_PREFIX_SUCCESS:CONFIGURATION_FILE_HAS_BEEN_UPDATED');
                }  else {
                    $msg .= '<span class="prefix_error">' . JText::_('COM_PREFIX_ERROR:CONFIGURATION_FILE_COULD_NOT_BE_UPDATE,PLEASE_MANUAL_UPDATE') . '</span>';
                }
            }
        } else {
            $msg .= '<span class="prefix_error">' . JText::_('COM_PREFIX_ERROR:TABLE_PREFIX_COULD_NOT_BE_UPDATE') . '</span>';
        }
    }
    ob_end_clean();
    JResponse::setHeader("Pragma", "no-cache");
    JResponse::setHeader("Expires","0");
    echo $msg;
    exit;
} // end function    
}

Answer 1

Not 100% this is your issue, but you have no display method and as a result you're also not calling the super class display method. Try changing this method:

public function __construct() {

To:

public function display($cachable = false, $urlparams = false) {
    require_once JPATH_COMPONENT . '/helpers/qtableprefix.php';
    $this->input = JFactory::getApplication()->input;
    $this->input->get('view', $this->input->get('view', 'tableprefix'));
    $view = $this->input->get('view');
    QTablePrefixHelper::addSubMenu((isset($view)) ? $view : '');
    parent::display($cachable, $urlparams);
    return $this
}

See if that corrects your issue.

Answer 2

Line 20 looks pretty messed up. I'm not sure what you are trying to do with it? In general though the error is because you haven't defined $this->input:

try using this instead:

public function __construct() {

    require_once JPATH_COMPONENT . '/helpers/qtableprefix.php';
    $this->input = JFactory::getApplication()->input;
    $this->input->get('view', $this->input->get('view', 'tableprefix'));
    parent::__construct();
    $view = $this->input->get('view');
    QTablePrefixHelper::addSubMenu((isset($view)) ? $view : '');
}

note that

$this->input->get('view', $this->input->get('view', 'tableprefix'));

won't do anything though as you are not assigning the input to a variable. As far as I can tell you could simply remove the line altogether