Extbase Property Mapping for arrays - typo3

Question

I want to use a Array Object inside a Fluid form using Property Mapper. The products are dynamic added if user clicks an "add_product" link:
<f:form action="property" name="newOrder" object="{newOrder}">
<f:for each="{newOrder.orderProduct}" as="orderProduct" iteration="iterator">
<f:form.hidden property="orderProduct.{iterator.index}.product" value="8" />
<h3>OrderProduct: {orderProduct.product.title}</h3>
</f:for>
<f:form.hidden name="add_product" value="1" />
<input type="submit" value="submit" />
</f:form>
What I get after submit is this exception.
Uncaught TYPO3 Exception #1297759968:
Exception while property mapping at property path "orderProduct.0":
Property "product" was not found in target object of type "MyVendor\MyShop\Domain\Model\Product".
The hidden field resolves to: <input name="tx_myshop_pi1[newOrder][orderProduct][0][product]" value="8" type="hidden"> (the static value of 8 is just to simplify the example)
I also tried key="key" instead of iterator, empty brackets orderProduct[], using name instead of property without result.
This is the (simplified) Debug output:
newOrder (MyVendor\MyShop\Domain\Model\ShopOrder)
=> orderProduct (TYPO3\CMS\Extbase\Persistence\ObjectStorage)
3222112 => MyVendor\MyShop\Domain\Model\OrderProduct
product => MyVendor\MyShop\Domain\Model\Product
uid => 8
title => 'Product1'
This is the Model Code:
ShopOrder https://pastebin.com/YN7X37ei
OrderProduct https://pastebin.com/zFyztLAQ
For the Property Mapper, I tried a lot of configurations without success. In my opinion this should work but it does not:
public function initializePropertyAction()
{
/** #var \TYPO3\CMS\Extbase\Property\PropertyMappingConfiguration $propertyMappingConfiguration */
$propertyMappingConfiguration = $this->arguments['newOrder']->getPropertyMappingConfiguration();
$propertyMappingConfiguration->allowAllProperties();
$propertyMappingConfiguration->setTypeConverterOption('TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter',
PersistentObjectConverter::CONFIGURATION_CREATION_ALLOWED,
TRUE);
$propertyMappingConfiguration->forProperty('orderProduct')->allowAllProperties();
$propertyMappingConfiguration->forProperty('orderProduct')->setTypeConverterOption(
'TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter',
PersistentObjectConverter::CONFIGURATION_CREATION_ALLOWED,
TRUE
);
//workaround from https://forge.typo3.org/issues/61628
for ($i = 0; $i < 99; $i++) {
$propertyMappingConfiguration->forProperty('orderProduct.' . $i)->allowAllProperties();
$propertyMappingConfiguration->forProperty('orderProduct.' . $i . '.*')->allowAllProperties();
$propertyMappingConfiguration->forProperty('orderProduct.' . $i)->setTypeConverterOption(
'TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter',
PersistentObjectConverter::CONFIGURATION_CREATION_ALLOWED,
TRUE
);
}
}

Answer 1

I solved it like this, in my case for a question with a dynamic number of answers having two fields, each:
$propertyMappingConfiguration = $this->arguments->getArgument('question')->getPropertyMappingConfiguration();
$propertyMappingConfiguration->skipProperties('category');
$propertyMappingConfiguration->allowProperties('answers');
$propertyMappingConfiguration->forProperty('answers.*')->allowProperties('answerField1', 'answerField2');
$propertyMappingConfiguration->allowCreationForSubProperty('answers.*');
$propertyMappingConfiguration->allowModificationForSubProperty('answers.*');