How can I display a message based upon the value of a config item

Question

I'm trying to show a warning based on robots being set to noindex or nofollow. I've copied the PHP Version quickicons plugin.

Here's my php file.

<?php
/**
 * @package     Joomla.Plugin
 * @subpackage  Quickicon.phpversioncheck
 *
 * @copyright   Copyright (C) 2005 - 2018 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

defined('_JEXEC') or die;

/**
 * Plugin to check if the robots configuration is correct filled in.
 *
 * @since  3.7.0
 */
class PlgQuickiconKoyRobots extends JPlugin
{

    /**
     * Application object.
     *
     * @var    JApplicationCms
     * @since  3.7.0
     */
    protected $app;

    /**
     * Load plugin language files automatically
     *
     * @var    boolean
     * @since  3.7.0
     */
    protected $autoloadLanguage = true;

    /**
     * Check what Robots.txt is set to and display an error if it's hiding the site.
     *
     * @param   string  $context  The calling context
     *
     * @return  void
     *
     * @since   3.7.0
     */
    public function onGetIcons($context)
    {
        if (!$this->shouldDisplayMessage())
        {
            return;
        }

        // $app = JFactory::getApplication();
        // $robots = $app->get('robots');
        $robots = $this->app->get('robots');

        /*
            Blank = index, follow
            noindex, follow
            index, nofollow
            noindex, nofollow
        */

        // $app->enqueueMessage('This is an error', 'error');
        $this->app->enqueueMessage('This is an error', 'error');
        if ($robots == "noindex, follow"){
            // Add a message to the message queue
            $this->app->enqueueMessage(JText::_('PLG_QUICKICONS_KOY_ROBOTS_NO_INDEX_FOLLOW'), 'error');
        }
        if ($robots == "index, nofollow"){
            // Add a message to the message queue
            $this->app->enqueueMessage(JText::_('PLG_QUICKICONS_KOY_ROBOTS_NO_INDEX_NO_FOLLOW'), 'error');
        }
        if ($robots == "noindex, nofollow"){
            // Add a message to the message queue
            $this->app->enqueueMessage(JText::_('PLG_QUICKICONS_KOY_ROBOTS_INDEX_NO_FOLLOW'), 'error');
        }
    }



    /**
     * Determines if the message should be displayed
     *
     * @return  boolean
     *
     * @since   3.7.0
     */
    private function shouldDisplayMessage()
    {
        // Only on admin app
        if (!$this->app->isClient('administrator'))
        {
            return false;
        }

        // Only if authenticated
        if (JFactory::getUser()->guest)
        {
            return false;
        }

        // Only on HTML documents
        if ($this->app->getDocument()->getType() !== 'html')
        {
            return false;
        }

        // Only on full page requests
        if ($this->app->input->getCmd('tmpl', 'index') === 'component')
        {
            return false;
        }

        // Only to com_cpanel
        if ($this->app->input->get('option') !== 'com_cpanel')
        {
            return false;
        }

        return true;
    }
}

It installs correctly and all of the language files show, so I'm pretty sure the error is within this file.

• No message displays.
• The plugin is activated.
• The robots text is set to a value that should show (noindex, nofollow)
• I am on the dashboard.

Answer 1

This

JFactory::getapp();

should be

JFactory::getApplication();

or because the app property has already been made protected above you can just use it like

$this->app->get('robots');

but the fact that it didn't throw a fatal error suggests to me that either you didn't enable the plugin after installation, or you weren't looking in the control panel where the quick icons appear.