Drupal 7 Module Development

Creating New Fields
In this simple case, all we're doing is creating two or three form elements for the
dimensions, one for each dimension, and a select box to set the units. The available
units are provided by a simple utility function that we also write:
function dimfield_units($unit = NULL) {
static $units;
if (empty($units)) {
$units = array(
'inches' => t('Inches'),
'feet' => t('Feet'),
'meters' => t('Meters'),
);
}
if ($unit) {
return isset($units[$unit]) ? $units[$unit] : '';
}
}
return $units;
That little utility function lets us get a consistent list of units we support anywhere
we need it, plus it provides an easy mapping from the "internal name" of a unit to a
translated human-friendly name.
It is important to note that the form elements we're creating are named exactly the
same as the columns of the dimensions field. Drupal needs the "processed form" value
to have the exact same "form element" names as the field columns so that it can save
them properly. What makes this a simple widget is that the form maps one-to-one to
the field definition, so we don't need to do any extra processing. At this point, we are
in essence done. Users will be able to select our widget, Drupal will handle the multivalue
logic for us, and save the data to the field, all without further interaction from us.
Complex widgets
Let's now look at the more complex widget. In this case, we will show all dimensions
together in a single text field so that the user need only fill in a single field.
First off, because our more complex widget has settings that we need to implement,
we use the widget_settings_form callback, given as follows:
function dimfield_field_widget_settings_form($field, $instance) {
$form = array();
$widget = $instance['widget'];
$settings = $widget['settings'];
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