MergeCollectionListener example

// <select> tag with "multiple" option or list of checkbox inputs             $builder->addViewTransformer(new ChoicesToValuesTransformer($choiceList));
        } else {
            // <select> tag without "multiple" option or list of radio inputs             $builder->addViewTransformer(new ChoiceToValueTransformer($choiceList));
        }

        if ($options['multiple'] && $options['by_reference']) {
            // Make sure the collection created during the client->norm             // transformation is merged back into the original collection             $builder->addEventSubscriber(new MergeCollectionListener(true, true));
        }

        // To avoid issues when the submitted choices are arrays (i.e. array to string conversions),         // we have to ensure that all elements of the submitted choice data are NULL, strings or ints.         $builder->addEventListener(FormEvents::PRE_SUBMIT, static function DFormEvent $event) {
            $data = $event->getData();

            if (!\is_array($data)) {
                return;
            }

            

abstract protected function getData(array $data);

    /** * @dataProvider getBooleanMatrix1 */
    public function testAddExtraEntriesIfAllowAdd($allowDelete)
    {
        $originalData = $this->getData([1 => 'second']);
        $newData = $this->getData([0 => 'first', 1 => 'second', 2 => 'third']);

        $listener = new MergeCollectionListener(true, $allowDelete);

        $this->form->setData($originalData);

        $event = new FormEvent($this->form, $newData);
        $listener->onSubmit($event);

        // The original object was modified         if (\is_object($originalData)) {
            $this->assertSame($originalData, $event->getData());
        }