How to implement many-to-many relationships in Sonata Media Bundle

sonata-admin, symfony

Solution

I had the same problem as you, but I've figured it out.

First of all, you might want to choose for a one-to-many/many-to-one relationship (using an intermediate entity) instead of a many-to-many relationship. Why? Because this allows for additional columns, such as a `position` column. This way you can reorder the images any way you want. In a many-to-many relationship, the link table only has two columns: the id's of the associated tables.

From the Doctrine documentation:

(...) frequently you want to associate additional attributes with an association, in which case you introduce an association class. Consequently, the direct many-to-many association disappears and is replaced by one-to-many/many-to-one associations between the 3 participating classes.

So I added this to my Product mapping file: (as you can see I'm using YAML as my configuration file format)

oneToMany:
    images:
        targetEntity: MyBundle\Entity\ProductImage
        mappedBy: product
        orderBy:
            position: ASC

And I created a new ProductImage mapping file:

MyBundle\Entity\ProductImage:
    type: entity
    table: product_images
    id:
        id:
            type: integer
            generator: { strategy: AUTO }
    fields:
        position:
            type: integer
    manyToOne:
        product:
            targetEntity: MyBundle\Entity\Product
            inversedBy: images
        image:
            targetEntity: Application\Sonata\MediaBundle\Entity\Media

Using the command line (`php app/console doctrine:generate:entities MyBundle`) I created / updated the corresponding entities (`Product` and `ProductImage`).

Next, I created/updated the Admin classes. ProductAdmin.php:

class ProductAdmin extends Admin
{
    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper
            // define other form fields
            ->add('images', 'sonata_type_collection', array(
                'required' => false
            ), array(
                'edit' => 'inline',
                'inline' => 'table',
                'sortable'  => 'position',
            ))
        ;
    }

ProductImageAdmin.php:

class ProductImageAdmin extends Admin
{
    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper
            ->add('image', 'sonata_type_model_list', array(
                'required' => false
            ), array(
                'link_parameters' => array(
                    'context' => 'product_image'
                )
            ))
            ->add('position', 'hidden')
        ;
    }

Don't forget to add both of them as services. If you don't want a link to the ProductImage form to be displayed on the dashboard, add the `show_in_dashboard: false` tag. (how you do this depends on the configuration format (yaml/xml/php) you use)

After this I had the admin form working correctly, however I still had some problems trying to save products. I had to perform the following steps in order to fix all problems:

First, I had to configure cascade persist operations for the Product entity. Again, how to do this depends on your configuration format. I'm using yaml, so in the `images` one-to-many relationship, I added the cascade property:

oneToMany:
    images:
        targetEntity: MyBundle\Entity\ProductImage
        mappedBy: product
        orderBy:
            position: ASC
        cascade: ["persist"]

That got it working (or so I thought), but I noticed that the `product_id` in the database was set to `NULL`. I solved this by adding `prePersist()` and `preUpdate()` methods to the `ProductAdmin` class:

public function prePersist($object)
{
    foreach ($object->getImages() as $image) {
        $image->setProduct($object);
    }
}

public function preUpdate($object)
{
    foreach ($object->getImages() as $image) {
        $image->setProduct($object);
    }
}

... and added a single line to the `addImages()` method of the `Product` entity:

public function addImage(\MyBundle\Entity\ProductImage $images)
{
    $images->setProduct($this);
    $this->images[] = $images;

    return $this;
}

This worked for me, now I can add, change, reorder, delete, etc. images to/from my Products.

Problem

Original source