Symfony CRUD controller - how does it works? - php

Question

I'm trying to understand how is Symfoy CRUD controllers works, i've googled a lot and can't find any answers.
So the question is, how does controller knows, which entity is passed to route?
For example:
In this index route, we are calling doctrine manager and then pulling all the comments from database.
/**
* Lists all Comment entities.
*
* #Route("/", name="admin_comment_index")
* #Method("GET")
*/
public function indexAction()
{
$em = $this->getDoctrine()->getManager();
$comments = $em->getRepository('AppBundle:Comment')->findAll();
return $this->render('comment/index.html.twig', array(
'comments' => $comments,
));
}
but at next "new" action we are not calling any doctrine instances.Controller seems alredy knows which entity is operating.
/**
* Creates a new Comment entity.
*
* #Route("/new", name="admin_comment_new")
* #Method({"GET", "POST"})
*/
public function newAction(Request $request)
{
$comment = new Comment();
$form = $this->createForm('AppBundle\Form\CommentType', $comment);
$form->handleRequest($request);
if ($form->isSubmitted() && $form->isValid()) {
$em = $this->getDoctrine()->getManager();
$em->persist($comment);
$em->flush();
return $this->redirectToRoute('admin_comment_show', array('id' => $comment->getId()));
}
return $this->render('comment/new.html.twig', array(
'comment' => $comment,
'form' => $form->createView(),
));
}
I guess it's because second route gets "Request" object, is entity stored in it? I'd like to have some deeper explanation.
UPDATE: "new" action seems clear to me now,it was a bad example of what i'm trying to figure, but let's see the "edit" action:
public function editAction(Request $request, Comment $comment)
{
$deleteForm = $this->createDeleteForm($comment);
$editForm = $this->createForm('AppBundle\Form\CommentType', $comment);
$editForm->handleRequest($request);
if ($editForm->isSubmitted() && $editForm->isValid()) {
$em = $this->getDoctrine()->getManager();
$em->persist($comment);
$em->flush();
return $this->redirectToRoute('admin_comment_edit', array('id' => $comment->getId()));
}
return $this->render('comment/edit.html.twig', array(
'comment' => $comment,
'edit_form' => $editForm->createView(),
'delete_form' => $deleteForm->createView(),
));
}
This time, form is already rendered with data in it, but we are only passing 'id" in request
edit
From where data comes this time? Seems like from comment object,which is passed into controller, but i dont see where it come from.
Sorry for my noobish questions and bad english!

Answer 1

I think you are making it complicated assuming controller knows what to do.
It's actually what code is written inside a controller defines what controller does. For example :
indexAction supposed to get you list of comments from database, hence you need to get EntityManager first to fetch the data. this controller doesn't deal with form as its not required.
newAction supposed to create a new instance of the Comment entity and generate a form to be filled up by user, when submitted Request parameter catches all data and saves to the database. hence, unless you get data from a submitted form, you don't need entity manager to deal with database.
Also, don't assume these are limited to what controller can do, You can customise any controller as per you requirement.
Hope it make sense.

Answer 2

newAction does get an EntityManager instance inside the if statement.
if ($form->isSubmitted() && $form->isValid()) {
$em = $this->getDoctrine()->getManager();
//...
And then it uses this manager to persist the object and flush.
When you load the newAction page, it created a new comment object, and sends that to the formbuilder. After that, it makes sure that the form data is placed onto the new Comment object, allowing it to be persisted.

Answer 3

In newAction function:
First, your form is mapped with your entity :
$comment = new Comment();
$form = $this->createForm('AppBundle\Form\CommentType', $comment);
So Symfony knows that you deal with Comment objects in your form
Then when you submit the form, handleRequest() recognizes this and immediately writes the submitted data back into the Comment object
Finally, if object is valid, you just have to save it in the database thanks to entityManager
So between the request and your formType Symfony knows what he wants

Answer 4

I was wondering the same when I created the first controller via generate:doctrine:crud.
As I'm new to symfony as well, what I state is still based on some assumptions. If I'm wrong, I'm thankful for any correction as it helps me learning.
The Kernel seems to recognises what your controller function accepts based on type hinting. By this, it determines whether your controller function accepts the Request object or not.
Further more, the arguments from the route are resolved and parsed with respect to the hinted types. This should
The magic is then done via Sensio\Bundle\FrameworkExtraBundle\Request\ParamConverter Class.
By type hinting your desired object Comment, the id parameter is converted to the associated object and loaded from your database.
By the way, what I couldn't figure out so far: is it possible to use a different order of parameters in my route than in my function?
e.g. is it possible to do
/user/{user_id}/{comment_id}
with
public function funWithUserComment( Request $request, Comment $comment, User $user)
{
//..
}
Hope, it helps you though.