function AjaxColorForm::buildForm

File

form_api_example/src/Form/AjaxColorForm.php, line 29

Class

AjaxColorForm

Implements the ajax demo form controller.

Namespace

Code

public function buildForm(array $form, FormStateInterface $form_state) {
    $form['description'] = [
        '#type' => 'item',
        '#markup' => $this->t('This form example demonstrates functioning of an AJAX callback.'),
    ];
    // The #ajax attribute used in the temperature input element defines an ajax
    // callback that will invoke the 'updateColor' method on this form object.
    // Whenever the temperature element changes, it will invoke this callback
    // and replace the contents of the 'color_wrapper' container with the
    // results of this method call.
    $form['temperature'] = [
        '#title' => $this->t('Temperature'),
        '#type' => 'select',
        '#options' => $this->getColorTemperatures(),
        '#empty_option' => $this->t('- Select a color temperature -'),
        '#ajax' => [
            // Could also use [get_class($this), 'updateColor'].
'callback' => '::updateColor',
            'wrapper' => 'color-wrapper',
        ],
    ];
    // Add a wrapper that can be replaced with new HTML by the ajax callback.
    // This is given the ID that was passed to the ajax callback in the '#ajax'
    // element above.
    $form['color_wrapper'] = [
        '#type' => 'container',
        '#attributes' => [
            'id' => 'color-wrapper',
        ],
    ];
    // Add a color element to the color_wrapper container using the value
    // from temperature to determine which colors to include in the select
    // element.
    $temperature = $form_state->getValue('temperature');
    if (!empty($temperature)) {
        $form['color_wrapper']['color'] = [
            '#type' => 'select',
            '#title' => $this->t('Color'),
            '#options' => $this->getColorsByTemperature($temperature),
        ];
    }
    // Add a submit button that handles the submission of the form.
    $form['actions'] = [
        '#type' => 'actions',
        'submit' => [
            '#type' => 'submit',
            '#value' => $this->t('Submit'),
        ],
    ];
    return $form;
}