Using #states ['required'] based on inputfor Drupal 8 , 9 , 10 , and 11

In this lesson, we delve into making form fields conditionally required using Drupal's Form API #states property. This powerful feature lets you dynamically adjust the form validation requirements based on user input, ensuring that important data is collected only when contextually relevant.

What is #states['required']?

The #states['required'] property allows you to set form fields as required dynamically. By associating this state with user interactions, you can enforce data collection rules that adapt to the input context. This approach ensures that fields are only mandatory when necessary, improving form usability and reducing unnecessary input from users.

Why Use Conditional Required Fields?

• Contextual Validation: Ensures that fields are mandatory only under certain conditions, tailored to user input.
• Enhanced User Experience: Improves user satisfaction by not overwhelming them with unnecessary required fields.
• Accurate Data Collection: Encourages precise data entry by matching form logic with user intent.

Example: Making Fields Conditionally Required

Consider a scenario where a registration form asks users if they require accommodation during an event. If the user indicates they do, additional details about accommodation preferences become mandatory.

function mymodule_registration_form(array &$form, \Drupal\Core\Form\FormStateInterface $form_state) {
    $form['need_accommodation'] = [
        '#type' => 'checkbox',
        '#title' => t('Do you require accommodation?'),
    ];

    $form['accommodation_details'] = [
        '#type' => 'textarea',
        '#title' => t('Please specify your accommodation details'),
        '#states' => [
            'visible' => [
                ':input[name="need_accommodation"]' => ['checked' => TRUE],
            ],
            'required' => [
                ':input[name="need_accommodation"]' => ['checked' => TRUE],
            ],
        ],
    ];

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

    return $form;
}

Explanation of the Code

Here's how this example works:

• The form includes a checkbox, need_accommodation, asking users if they require accommodation.
• A text area, accommodation_details, becomes visible and required when the above checkbox is checked. This condition is managed using two #states properties: 'visible' and 'required'.
• These states ensure that users are prompted to provide details about their accommodation plans only if they indicate a need, thus avoiding unnecessary data collection.

Advantages of Dynamic Required States

By using #states['required'], you ensure your form collects all necessary information while remaining concise and user-friendly. This approach also minimizes form abandonment rates by not forcing users to provide data irrelevant to their use case.

Conclusion

Conditionally required fields in Drupal form building add a dynamic layer, ensuring forms adapt to the input context. This flexibility leads to better data integrity and enhances user interaction with the form.

What's Next?

In the next lesson, we'll introduce logical operators like and, or, and xor within #states logic, allowing you to craft even more sophisticated conditional logic for your forms. Stay tuned to learn how to integrate complex conditional rules seamlessly into your Drupal forms.