Question about JTable::getInstance in libraries/joomla/table/table.php file

Question

I was trying to read and understand some joomla core PHP code when I came across this function. It is located in libraries/joomla/table/table.php line 268. At the end of the function in line 305, it returns an object created by $tableClass, what I don't understand is, where is this $tableClass class defined? Following is a complete list of the function:

public static function getInstance($type, $prefix = 'JTable', $config = array())
{
    // Sanitize and prepare the table class name.
    $type       = preg_replace('/[^A-Z0-9_\.-]/i', '', $type);
    $tableClass = $prefix . ucfirst($type);

    // Only try to load the class if it doesn't already exist.
    if (!class_exists($tableClass))
    {
        // Search for the class file in the JTable include paths.
        jimport('joomla.filesystem.path');

        $paths = self::addIncludePath();
        $pathIndex = 0;

        while (!class_exists($tableClass) && $pathIndex < count($paths))
        {
            if ($tryThis = JPath::find($paths[$pathIndex++], strtolower($type) . '.php'))
            {
                // Import the class file.
                include_once $tryThis;
            }
        }

        if (!class_exists($tableClass))
        {
            // If we were unable to find the class file in the JTable include paths, raise a warning and return false.
            JLog::add(JText::sprintf('JLIB_DATABASE_ERROR_NOT_SUPPORTED_FILE_NOT_FOUND', $type), JLog::WARNING, 'jerror');

            return false;
        }
    }

    // If a database object was passed in the configuration array use it, otherwise get the global one from JFactory.
    $db = isset($config['dbo']) ? $config['dbo'] : JFactory::getDbo();

    // Instantiate a new table class and return it.
    return new $tableClass($db);
}

Answer 1

Joomla is flexible and relaxed with the physical storage of Table-Classes.

The dirty way (I think you do not use a debugger) is to rewrite the following line

$paths = self::addIncludePath();

to:

var_dump($paths = self::addIncludePath());

So you will see the paths where the Table-Class are stored.

3rd-party components tells Joomla where their own tables are located. Mostly like the following.

JTable::addIncludePath('/administrator/components/componentname/tables');

If you are searching for a 3rd-party component table, have a look in the /administrator/componentname/tables