Handle form data by myself - php

Question

I built a form with createFormBuilder
$form = $this->createFormBuilder($post)
->add("name", TextType::class, array("label"=>"Article Title"))
->add("content", TextareaType::class, array("label"=>"Article Content"))
->add("categories",
EntityType::class,
array(
"class" => Category::class,
"choice_label" => "name",
"multiple" => true,
"label" => "Article Category",
"required" => false
)
)
->add("attachments", TextType::class, array("required"=>false))
->add("submit", SubmitType::class, array("label"=>"Add new article"))
->getForm();
the "attachments" variable is an entity variable, I want to get a json string from the form and search the database by myself, like this:
$em = $this->getDoctrine()->getManager();
$attachmentsRepository = $em->getRepository(Attachment::class);
$attachments = $post->getAttachments();
$json = json_decode($attachments);
$dataSize = sizeof($json);
for ($i = 0; $i < $dataSize; $i ++) {
$attachment = $attachmentsRepository->find($json[$i]->getId());
$post->addAttachments($attachment);
}
$em->persist($post);
$em->flush();
However, there is the error hint said that:
Could not determine access type for property "attachments" in class
"App\Entity\Post".
I don't know how to solve this problem, if I add a #ORM\Column(type="string") in my Entity the json string will also be stored, I think this is not a good solution.
How do I modify my code?

Answer 1

First of all to get rid of the error you need to add mapped => false to the field options of your attachments field.
If the attachments fields is configured as a mapped field the form component will look for a setAttachments() method or a public property attachments in your Post Entity to set the value - which do not exist in your Post entity. That's why you get the error message:
Could not determine access type for property "attachments" in class "App\Entity\Post".
In order to transform the submitted JSON string to Attachment entities yourself you need a custom data transformer!
A good example how create and use a data transformer can be found in the documentation chapter How to Use Data Transformers.
A clean solution would involve the attachments field being a CollectionType of EntityType, sending the whole form as a JSON POST request and using i.e FOSRestBundle's fos_rest.decoder.jsontoform body listener to decode the JSON request to a form.
The documentation for FOSRestBundle's body listener support can be found here.