ManyToMany: The Inverse Side of the Relationship

Hi!

I don't really know what is happening but I am having a problem with the inverse side of the relationship. I have categories and products like below. The problem is that it works when I save products in a category but not the inverse. I tried in my controller to $em->flush() without a parameter but it tells me:
<blockquote>A new entity was found through the relationship 'AppBundle\Entity\Product#categories' that was not configured to cascade persist operations for entity:
AppBundle\Entity\Category@00000000565496d3000000017d6c6077. To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or configure cascade persist this association in the mapping for example @ManyToOne(..,cascade={"persist"}). If you cannot find out which entity causes the problem implement 'AppBundle\Entity\Category#__toString()' to get a clue".
</blockquote>

/**
 * @ORM\ManyToMany(targetEntity="Category", mappedBy="products")
 */
private $categories;

public function __construct()
{
    $this->categories = new ArrayCollection();
}

/**
 * @return ArrayCollection|Category[]
 */
public function getCategories()
{
    return $this->categories;
}

public function addCategory(Category $category)
{
    if ($this->categories->contains($category)) {
        return;
    }

    $this->categories[] = $category;

    // not needed for persistence, just keeping both sides in sync
    $category->addProduct($this);
}

public function removeCategory(Category $category)
{
    if (!$this->categories->contains($category)) {
        return;
    }

    $this->categories->removeElement($category);

    // not needed for persistence, just keeping both sides in sync
    $category->removeProduct($this);
}

and

/**
 * @ORM\ManyToMany(targetEntity="Product", inversedBy="categories", fetch="EXTRA_LAZY")
 * @ORM\JoinTable(name="categories_products")
 */
private $products;

public function __construct()
{
    $this->products = new ArrayCollection();
}

/**
 * @return ArrayCollection|Product[]
 */
public function getProducts()
{
    return $this->products;
}

public function addProduct(Product $product)
{
    if ($this->products->contains($product)) {
        return;
    }

    $this->products[] = $product;

    // not needed for persistence, just keeping both sides in sync
    $product->addCategory($this);
}

public function removeProduct(Product $product)
{
    if (!$this->products->contains($product)) {
        return;
    }

    $this->products->removeElement($product);

    // not needed for persistence, just keeping both sides in sync
    $product->removeCategory($this);
}

Let me know if you need more details to help me to solve this problem.

Thanks loads guys!

James

Hey James,

Looks like you need to call persist() on Category entity which you add to collection. Don't forget that Doctrine requires calling persist() on new entities before calling flush().

Cheers!

Thanks for the fast reply! You guys are awesome!
I did as you said so I am updating the products and because I keep both side synced, I am also updating the categories. So I tried to persist products then persist categories then flush but I still get the following error:

A new entity was
found through the relationship 'AppBundle\Entity\Product#categories'
that was not configured to cascade persist operations for entity:
AppBundle\Entity\Category@000000006d8a552300000001007fe7fa. To solve
this issue: Either explicitly call EntityManager#persist() on this
unknown entity or configure cascade persist this association in the
mapping for example @ManyToOne(..,cascade={"persist"}). If you cannot
find out which entity causes the problem implement
'AppBundle\Entity\Category#__toString()' to get a clue.

Here is my code in the controller:

if ($formCategory->isSubmitted() && $formCategory->isValid()) {

// Save category changes
$category->setName($formCategory['name']->getData());
$category->setSub($formCategory['sub']->getData());
$category->setSlug($formCategory['slug']->getData());
$category->setMetaTitle($formCategory['metaTitle']->getData());
$category->setMetaKeywords($formCategory['metaKeywords']->getData());
$category->setMetaDescription($formCategory['metaDescription']->getData());
$category->setDescription($formCategory['description']->getData());

if ($formCategory['image']->getData()){

$imageSaver = new ImageService();

$imageName = $imageSaver->imageSaveAction(
$formCategory['image']->getData(),
$formCategory['name']->getData(),
$this->getParameter('images_directory')
);

$category->setImageName($imageName);
}

foreach ($category->getProducts() as $product) {
$category->removeProduct($product);
}

if (count($formCategory['products']->getData())){

foreach ($formCategory['products']->getData() as $product) {
$category->addProduct($product);
$em->persist($product);
}

}

$em->persist($category);
$em->flush();

$this->addFlash('success', 'Category updated');

return $this->redirectToRoute('categories_view', array('id' => $category->getId()));

}

Hey James Davison
Have you tried configuring "cascade" on persist? or you have a special reason to don't do it?
Another question, why are you removing all products from the category?

Thanks for the tip Diego! Added cascade and it does the trick. If I don't remove all products from category first then if I just delete products from the category it does not work. Maybe do you know of a quick way to identify the products which are not present anymore which need to be deleted; something to check the difference.

That's great!
I need to know a bit more about the relationship between category and product, can you have products without a category?

Hi! Thanks for the quick answer,
it is a many to many and products or categories can be alone.

The entities code is in my first message.

Thanks again!

If you dump `$category->getProducts()` and `$formCategory['products']->getData()`
Are there any differences?

Do you have this code in any public repository? I would like to check it in more detail

Let me add you as a collaborator on Github if this is alright with you.

sure no problem, find me as Larzuk91

I have sent you an invite.

Thanks again

Hey James, I could see your invitation, but for some reason I cannot see your organization into my list =/
What's the name of your org/repo?

I seem to get a problem with my self referenced many to many relation in between products.
I changed the relation to a many to many unidirectional which works on the frontend but do not know how to incorporated to the form to add or delete related products to a product.
The error coming up is:
Entities passed to the choice field must be managed. Maybe persist them in the entity manager?

https://github.com/connectj...

Just sent you another message on my github, the related products don't seem to work when passing the object to the form. Could you help me please?

Hi,

How would you approach ManyToMany relationship on the same entity. For example, if i am having entity Course and would like to have field represent the prerequisites courses of that Course which are from the same entity? what is the best way to implement this?

Thank you, much appreciated.

Hey Mohammad Althayabeh

I can think in two options, but to know which one is better for you, deppends on how are you planning to work with your objects

1) set a self referenced ManyToMany relationship (is like you said), you can get a better idea of how to achieve it here: http://docs.doctrine-projec... but I don't think you need to make it bidirectional

2) Create a new entity called something like `PrerequisiteCourseGroup` which will hold the Course and a list of (another new entity) `PrerequesiteCourse`, this entity will only have the reference of a Course (the prerequesite course)
So, in this case, given a Course, you can query for a PrerequisiteCourseGroup object and then ask him to give you the list of all prerequisite courses

Second approach is kind of confusing but it's nice if you don't want to alter your current course schema

Cheers!