Implements \Drupal\Core\Form\FormInterface::submitForm().
Overrides FormInterface::submitForm
public function submitForm(array &$form, array &$form_state) {
drupal_set_message(t('The FormTestControllerObject::submitForm() method was used for this form.'));
config('form_test.object')
->set('bananas', $form_state['values']['bananas'])
->save();
}