如何建立学说联系？

Question

I know that association property in entity is implements \\Doctrine\\Common\\Collections\\Collection . I know that in constructor such properties should be initialized:

$this->collection = new \\Doctrine\\Common\\Collections\\ArrayCollection()

I know that I can modify collections using ArrayCollection#add() and ArrayCollection#remove() . However I have a different case.

Suppose I have a new simple array of associative entities. Using existing methods I need to check every element in array: if entity collection has it. If no - add array element to entity collection. In addition to this, I need to check every element in entity collection. If any collection element is absent in new array, then I need to remove it from collection. So much work to do trivial thing.

What I want? To have the setProducts method implemented:

class Entity {
  private $products;

  // ... constructor

  public function setProducts(array $products)
  {
    // synchronize $products with $this->products
  }
}

I tried: $this->products = new ArrayCollection($products) . However this makes doctrine remove all products and add those ones from $products parameter. I want similar result but without database queries.

Is there any built in solution in Doctrine for such case?

Edit : I would like to have a method in ArrayCollection like fromArray which would merge elements in collections removing unneeded. This would just duplicate using add/remove calls for each element in collection argumen manually.

Answer 1

Doctrine collections do not have a "merge"-feature that will add/remove entities from an array or Collection in another Collection.

If you want to "simplify" the manual merge process you describe using add/remove, you could use array_merge assuming both arrays are not numeric, but instead have some kind of unique key, eg the entity's spl_object_hash :

public function setProducts(array $products)
{
    $this->products = new ArrayCollection(
        array_merge(
            array_combine(
                array_map('spl_object_hash', $this->products->toArray()),
                $this->products->toArray()
            ),
            array_combine(
                array_map('spl_object_hash', $products),
                $products->toArray()
            )
        )
    );
}

You might want to use the product id instead of spl_object_hash as 2 products with the same id, but created as separate entities - eg one through findBy() in Doctrine and one manually created with new Product() - will be recognized as 2 distinct products and might cause another insert-attempt.

Since you replace the original PersistentCollection holding your previously fetched products with a new ArrayCollection this might still result in unneeded queries or yield unexpected results when flushing the EntityManager, though. Not to mention, that this approach might be harder to read than explicitly calling addElement/removeElement on the original Collection instead.

Answer 2

I would approach it by creating my own collection class that extends Doctrine array collection class:

use Doctrine\Common\Collections\ArrayCollection;

class ProductCollection extends ArrayCollection
{
}

In the entity itself you would initialise it in the __constructor :

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

Here, Doctrine will you use your collection class for product results. After this you could add your own function to deal with your special merge, perhaps something:

public function mergeProducts(ProductCollection $products): ProductCollection
{
    $result = new ProductCollection();
    foreach($products as $product) {
        $add = true;
        foreach($this->getIterator() as $p) {
            if($product->getId() === $p->getId()) {
                $result->add($product);
                $add = false;
            }
        }
        if($add) {
            $result->add($product);
        }
    }
    return $result;
}

It will return a brand new product collection, that you can replace your other collection in the entity. However, if the entity is attached and under doctrine control, this will render SQL at the other end, if you want to play with the entity without risking database updates you need to detach the entity:

$entityManager->detach($productEntity);

Hopes this helps