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<?php
namespace Drupal\Core\Render\Element;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Render\Element;
/**
* Provides a form element for a drop-down menu or scrolling selection box.
*
* Properties:
* - #options: An associative array, where the keys are the values for each
* option, and the values are the option labels to be shown in the drop-down
* list. If a value is an array, it will be rendered similarly, but as an
* optgroup. The key of the sub-array will be used as the label for the
* optgroup. Nesting optgroups is not allowed.
* - #empty_option: (optional) The label to show for the first default option.
* By default, the label is automatically set to "- Select -" for a required
* field and "- None -" for an optional field.
* - #empty_value: (optional) The value for the first default option, which is
* used to determine whether the user submitted a value or not.
* - If #required is TRUE, this defaults to '' (an empty string).
* - If #required is not TRUE and this value isn't set, then no extra option
* is added to the select control, leaving the control in a slightly
* illogical state, because there's no way for the user to select nothing,
* since all user agents automatically preselect the first available
* option. But people are used to this being the behavior of select
* controls.
* @todo Address the above issue in Drupal 8.
* - If #required is not TRUE and this value is set (most commonly to an
* empty string), then an extra option (see #empty_option above)
* representing a "non-selection" is added with this as its value.
* - #multiple: (optional) Indicates whether one or more options can be
* selected. Defaults to FALSE.
* - #default_value: Must be NULL or not set in case there is no value for the
* element yet, in which case a first default option is inserted by default.
* Whether this first option is a valid option depends on whether the field
* is #required or not.
* - #required: (optional) Whether the user needs to select an option (TRUE)
* or not (FALSE). Defaults to FALSE.
* - #size: The size of the input element in characters.
*
* Usage example:
* @code
* $form['example_select'] = [
* '#type' => 'select',
* '#title' => $this->t('Select element'),
* '#options' => [
* '1' => $this->t('One'),
* '2' => [
* '2.1' => $this->t('Two point one'),
* '2.2' => $this->t('Two point two'),
* ],
* '3' => $this->t('Three'),
* ],
* ];
* @endcode
*
* @FormElement("select")
*/
class Select extends FormElement {
/**
* {@inheritdoc}
*/
public function getInfo() {
$class = get_class($this);
return [
'#input' => TRUE,
'#multiple' => FALSE,
'#process' => [
[$class, 'processSelect'],
[$class, 'processAjaxForm'],
],
'#pre_render' => [
[$class, 'preRenderSelect'],
],
'#theme' => 'select',
'#theme_wrappers' => ['form_element'],
'#options' => [],
];
}
/**
* Processes a select list form element.
*
* This process callback is mandatory for select fields, since all user agents
* automatically preselect the first available option of single (non-multiple)
* select lists.
*
* @param array $element
* The form element to process.
* @param \Drupal\Core\Form\FormStateInterface $form_state
* The current state of the form.
* @param array $complete_form
* The complete form structure.
*
* @return array
* The processed element.
*
* @see _form_validate()
*/
public static function processSelect(&$element, FormStateInterface $form_state, &$complete_form) {
// #multiple select fields need a special #name.
if ($element['#multiple']) {
$element['#attributes']['multiple'] = 'multiple';
$element['#attributes']['name'] = $element['#name'] . '[]';
}
// A non-#multiple select needs special handling to prevent user agents from
// preselecting the first option without intention. #multiple select lists do
// not get an empty option, as it would not make sense, user interface-wise.
else {
// If the element is set to #required through #states, override the
// element's #required setting.
$required = isset($element['#states']['required']) ? TRUE : $element['#required'];
// If the element is required and there is no #default_value, then add an
// empty option that will fail validation, so that the user is required to
// make a choice. Also, if there's a value for #empty_value or
// #empty_option, then add an option that represents emptiness.
if (($required && !isset($element['#default_value'])) || isset($element['#empty_value']) || isset($element['#empty_option'])) {
$element += [
'#empty_value' => '',
'#empty_option' => $required ? t('- Select -') : t('- None -'),
];
// The empty option is prepended to #options and purposively not merged
// to prevent another option in #options mistakenly using the same value
// as #empty_value.
$empty_option = [$element['#empty_value'] => $element['#empty_option']];
$element['#options'] = $empty_option + $element['#options'];
}
}
return $element;
}
/**
* {@inheritdoc}
*/
public static function valueCallback(&$element, $input, FormStateInterface $form_state) {
if ($input !== FALSE) {
if (isset($element['#multiple']) && $element['#multiple']) {
// If an enabled multi-select submits NULL, it means all items are
// unselected. A disabled multi-select always submits NULL, and the
// default value should be used.
if (empty($element['#disabled'])) {
return (is_array($input)) ? array_combine($input, $input) : [];
}
else {
return (isset($element['#default_value']) && is_array($element['#default_value'])) ? $element['#default_value'] : [];
}
}
// Non-multiple select elements may have an empty option prepended to them
// (see \Drupal\Core\Render\Element\Select::processSelect()). When this
// occurs, usually #empty_value is an empty string, but some forms set
// #empty_value to integer 0 or some other non-string constant. PHP
// receives all submitted form input as strings, but if the empty option
// is selected, set the value to match the empty value exactly.
elseif (isset($element['#empty_value']) && $input === (string) $element['#empty_value']) {
return $element['#empty_value'];
}
else {
return $input;
}
}
}
/**
* Prepares a select render element.
*/
public static function preRenderSelect($element) {
Element::setAttributes($element, ['id', 'name', 'size']);
static::setAttributes($element, ['form-select']);
return $element;
}
}