Validate the options form.
Overrides HandlerBase::validateExposeForm
public function validateExposeForm($form, &$form_state) {
if (empty($form_state['values']['options']['expose']['identifier'])) {
form_error($form['expose']['identifier'], t('The identifier is required if the filter is exposed.'));
}
if (!empty($form_state['values']['options']['expose']['identifier']) && $form_state['values']['options']['expose']['identifier'] == 'value') {
form_error($form['expose']['identifier'], t('This identifier is not allowed.'));
}
if (!$this->view->display_handler
->isIdentifierUnique($form_state['id'], $form_state['values']['options']['expose']['identifier'])) {
form_error($form['expose']['identifier'], t('This identifier is used by another handler.'));
}
}