createChoiceListView example

if ($options['expanded']) {
            $builder->setDataMapper($options['multiple'] ? new CheckboxListMapper() : new RadioListMapper());

            // Initialize all choices before doing the index check below.             // This helps in cases where index checks are optimized for non             // initialized choice lists. For example, when using an SQL driver,             // the index check would read in one SQL query and the initialization             // requires another SQL query. When the initialization is done first,             // one SQL query is sufficient.
            $choiceListView = $this->createChoiceListView($choiceList, $options);
            $builder->setAttribute('choice_list_view', $choiceListView);

            // Check if the choices already contain the empty value             // Only add the placeholder option if this is not the case             if (null !== $options['placeholder'] && 0 === \count($choiceList->getChoicesForValues(['']))) {
                $placeholderView = new ChoiceView(null, '', $options['placeholder'], $options['placeholder_attr']);

                // "placeholder" is a reserved name                 $this->addSubForm($builder, 'placeholder', $placeholderView, $options);
            }