Drupal 7 Module Development

Creating New Fields
During the validation phase of the form submission, this function will be called
with the element it is attached to (the height_width_depth element) and the
$form_state variable, which is passed by reference so that we can modify it. The
first thing we check is that we're not displaying this widget on the field configuration
page. If so, we don't bother validating it because nothing will be saved anyway.
Then, we check to see how many dimensions we're dealing with since the logic will
be slightly different. We then iterate over each submitted value and, assuming that
it has the requisite × character in it, break up the submitted string into three integers.
The explode() function in PHP will take a string and split it into an array using
the first parameter as a delimiter, while the list() operator will assign that array
to two or three separate variables for us. We then take those values and actively
set the height, width, units, and potential depth values within the form state using
form_set_value().
While it seems odd to use the validation step to manipulate the form data, it is the
only place that the form API allows us to do so. The net result is that we create new
values in the $form_state collection that match up with the columns in our field.
When Drupal submits the widget, it will look through the $form_state for variables
that match the names of the columns in the field. It doesn't care that we put those
values there ourselves, just that they exist is what matters. The original string still
exists in the height_width_depth variable, but Drupal will just ignore it.
We are also going to do a little custom theming to our combined widget. Note the
following lines:
$element['dimfield_combined_wrapper']['#theme'] = 'dimfield_combined_
wrapper';
$element['dimfield_combined_wrapper']['#attached']['css'][] = drupal_
get_path('module', 'dimfield') . '/dimfield-admin.css';
The first line tells the rendering system to use a theme hook named dimfield_
combined_wrapper to render everything that appears under $element['dimfield_
combined_wrapper']. The second tells the system to also load a particular CSS file
whenever this form element is displayed. In our case we'll do something simple and
just stick the two form elements—height_width_depth and units —into a wrapped
set of divs:
function dimfield_theme() {
return array(
'dimfield_combined_wrapper' => array(
'render element' => 'element',
),
);
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