function Autotextfields::buildForm

This form has two checkboxes which the user can check in order to then reveal the first and/or last name text fields.

We could perform this behavior with #states. We might not want to if, for instance, we wanted to require a name, but let the user choose whether to enter first or last or both.

For all the requests this class gets, the buildForm() method will always be called. If an AJAX request comes in, the form state will be set to the state the user changed that caused the AJAX request. So if the user enabled one of our checkboxes, it will be checked in $form_state.

Overrides FormInterface::buildForm

File

modules/ajax_example/src/Form/Autotextfields.php, line 37

Class

Autotextfields

Show textfields based on AJAX-enabled checkbox clicks.

Namespace

Code

public function buildForm(array $form, FormStateInterface $form_state) {
    $form['description'] = [
        '#type' => 'item',
        '#markup' => $this->t('This form demonstrates changing the status of form elements through AJAX requests.'),
    ];
    $form['ask_first_name'] = [
        '#type' => 'checkbox',
        '#title' => $this->t('Ask me my first name'),
        '#ajax' => [
            'callback' => '::textfieldsCallback',
            'wrapper' => 'textfields-container',
            'effect' => 'fade',
        ],
    ];
    $form['ask_last_name'] = [
        '#type' => 'checkbox',
        '#title' => $this->t('Ask me my last name'),
        '#ajax' => [
            'callback' => '::textfieldsCallback',
            'wrapper' => 'textfields-container',
            'effect' => 'fade',
        ],
    ];
    // Wrap textfields in a container. This container will be replaced through
    // AJAX.
    $form['textfields_container'] = [
        '#type' => 'container',
        '#attributes' => [
            'id' => 'textfields-container',
        ],
    ];
    $form['textfields_container']['textfields'] = [
        '#type' => 'fieldset',
        '#title' => $this->t("Generated text fields for first and last name"),
        '#description' => $this->t('This is where we put automatically generated textfields'),
    ];
    // This form is rebuilt on all requests, so whether or not the request comes
    // from AJAX, we should rebuild everything based on the form state.
    // Checkbox values are expressed as 1 or 0, so we have to be sure to compare
    // type as well as value.
    if ($form_state->getValue('ask_first_name', NULL) === 1) {
        $form['textfields_container']['textfields']['first_name'] = [
            '#type' => 'textfield',
            '#title' => $this->t('First Name'),
            '#required' => TRUE,
        ];
    }
    if ($form_state->getValue('ask_last_name', NULL) === 1) {
        $form['textfields_container']['textfields']['last_name'] = [
            '#type' => 'textfield',
            '#title' => $this->t('Last Name'),
            '#required' => TRUE,
        ];
    }
    $form['textfields_container']['submit'] = [
        '#type' => 'submit',
        '#value' => $this->t('Click Me'),
    ];
    return $form;
}