SubformStateInterface

Stores information about the state of a subform.

In the context of Drupal's Form API, a subform is a form definition array that will be nested into a "parent" form. For instance:

$subform = [
  'method' => [
    '#type' => 'select',
    // …
  ],
];
$form = [
  // …
  'settings' => $subform,
];

All input fields nested under "settings" are then considered part of that "subform". The concept is used mostly when the subform is defined by a different class (potentially even in a different module) than the parent form. This is often the case for plugins: a plugin's buildConfigurationForm() would then be handed an instance of this interface as the second parameter.

The benefit of doing this is that the plugin can then just define the form – and use the form state – as if it would define a "proper" form, not nested in some other form structure. This means that it won't have to know the key(s) under which its form structure will be nested – for instance, when retrieving the form values during form validation or submission.

Contrary to "proper" forms, subforms don't translate to a <form> tag in the HTML response. Instead, they can only be discerned in the HTML code by the nesting of the input tags' names.

Hierarchy

• interface \Drupal\Core\Form\FormStateInterface
  • interface \Drupal\Core\Form\SubformStateInterface

See also

\Drupal\Core\Plugin\PluginFormInterface::buildConfigurationForm()

File

core/lib/Drupal/Core/Form/SubformStateInterface.php, line 42

Namespace

Drupal\Core\Form

Members