Drupal 7: AJAX Form Update issue

Question

I have the following elements defined in my form hook:

$form['touchpointdivision'] = array(
    '#type' => 'select',
    '#title' => t('Division'),
    '#options' => $divisions,
    '#required' => TRUE,
    '#ajax' => array(
        'event' => 'change',
        'wrapper' => 'department-wrapper',
        'callback' => 'touchpoints_dept_callback',
        'method' => 'replace'
    )
);

$form['touchpointdepartment'] = array(
    '#type' => 'select',
    '#title' => t('Department'),
    '#prefix' => '<div id="department-wrapper">',
    '#suffix' => '</div>',
    '#options' => _get_departments($selected),
    '#required' => TRUE
);

Here's the callback:

function touchpoints_dept_callback($form, $form_state){
    return $form('touchpointdepartment');
}

When I change an item in the first dropdown I get the following error:

"Fatal error: Function name must be a string in /cmi/sites/all/modules/touchpoints/touchpoints.module on line 203"

What am I missing in this declaration?

Answer 1

Wow, dumb mistake. In the callback the fieldname should be in brackets not parentheses. So:

function touchpoints_dept_callback($form, $form_state){
    return $form('touchpointdepartment');
}

should be

function touchpoints_dept_callback($form, $form_state){
    return $form['touchpointdepartment'];
}