Implementing #states for dynamic visibility in Form Apifor Drupal 8 , 9 , 10 , and 11

In the previous lesson, we explored how to use AJAX in Drupal forms to enhance user interaction by allowing form submissions to process asynchronously. Building on this foundation, we will now delve into the use of the #states property in Drupal Form API. This feature empowers you to add dynamic behavior to your forms, such as showing or hiding certain fields based on user input.

Understanding #states

#states is a powerful feature of the Drupal Form API that allows you to make form elements react dynamically to change in another part of the form interface. This is done without writing any JavaScript code yourself, as Drupal handles the JavaScript generation necessary to execute these changes.

Why Use #states for Dynamic Visibility?

• Enhanced User Experience: Dynamic visibility ensures that users are only presented with relevant options based on their previous selections.
• Streamlined Interface: Keeps forms tidy by avoiding an overload of visible options, showing only applicable fields.
• No JavaScript Knowledge Required: Utilizes Drupal's built-in capabilities, reducing the need to manually write JavaScript.

Implementing #states in an Example Form

Let's create a scenario where you have a form with a checkbox to indicate whether additional information is required. Depending on the checkbox status, a text field for entering this additional information will be displayed.

function mymodule_form_with_states(array &$form, \Drupal\Core\Form\FormStateInterface $form_state) {
    $form['need_info'] = [
        '#type' => 'checkbox',
        '#title' => t('Need additional information?'),
    ];

    $form['extra_info'] = [
        '#type' => 'textfield',
        '#title' => t('Additional Information'),
        '#states' => [
            'visible' => [
                ':input[name="need_info"]' => ['checked' => TRUE],
            ],
        ],
    ];

    $form['submit'] = [
        '#type' => 'submit',
        '#value' => t('Submit'),
    ];

    return $form;
}

Explanation of the Code

In the form above:

• The checkbox element need_info asks whether the user needs additional information.
• The text field extra_info will only be displayed when the checkbox is checked. This behavior is managed through the #states property, which includes a 'visible' key.
• The 'visible' rule listens to the need_info checkbox. It uses the selector ':input[name="need_info"]' to track its state and shows the extra_info field when checked.

Benefits of Using #states

With #states, you improve the standard of your Drupal forms by ensuring that users engage with a more interactive and adaptive interface. This can potentially reduce form submission errors and enhance user satisfaction.

What's Next?

In the next lesson, we will focus on how to use various types of conditions with the #states['visible'] property to enable more sophisticated dynamic behaviors based on multiple form elements. Stay tuned!