Why $query = new JDatabaseQuery; but not $query = &new JDatabaseQuery; ?
In ../models/fields/helloworld.php on line 29
If you use the line, $query = new JDatabaseQuery;, component works, but when helloworlds is added as menu item it causes the following error when item is clicked:
Fatal error: Cannot instantiate abstract class JDatabaseQuery in C:\xampp\htdocs\test_site\administrator\components\com_helloworld\models\fields\helloworld.php on line 29
Reverting back to code from part 11, $query = $db->getQuery(true);, does not throw error.
Just an observation.
People who are using Joomla >= 2.5.5. will probably encounter a problem with categories menu - buttons for basic user actions missing (such as "New", "Edit" etc.) The solution can be found here: http://forum.joomla.org/viewtopic.php?f=642&t=730171