symfony2教义关系一对一

Question

I have 2 questions.

My first question comes from the doc of doctrine what is "exactly" the difference between the one-to-one unidirectional and the one-to-one bidirectional and when to use either of them?

Secondly I have a one-to-one as such

/**
 * @ORM\OneToOne(targetEntity="App\PurchaseBundle\Entity\Status", cascade={"persist"})
 * @ORM\JoinColumn(nullable=false)
 */
private $status;

When i try to save the form i have an error :

Integrity constraint violation: 1062 Duplicate entry '1' for key 'UNIQ_9861B36D6BF700BD' 

I understood from the doc that I need to do this relationship bidirectional but I dont see why. All I want is to remove the unique and replace it by index.

Thanks

PS : Just in case it might help. I have an entity Purchase which at the start will have a status of 'order_created' and will be updated in back office at different process.

Answer 1

To answer at your first question I'll take an example : If you have a User related (with a one to one unidirectionnal relation) to a Car. In this case if you have your user you'll be able to find the car he owns. But if you have the car you won't be able to find the User who owns this car. The bidirectionnal permit you to with your object car find your User.

In the first case this code will works :

$user->getCar();

But this one won't be possible :

$car->getUser();

The bidirectionnal allow you to execute both of them.

Hope this help to understand the concept.