Question

Can somebody explain me why UniqueEntity constraint class defines:

// ...

public $service = 'doctrine.orm.validator.unique';

public function validatedBy()
{
    return $this->service;
}

//...

And not simply:

public function validatedBy()
{
    return "UniqueEntityValidator";
}

UniqueEntityValidator class exists and has all the logic it needs. Whats the point of service here?

I’m asking this because now I cannot use UniqueEntity outside Symfony framework due to some dependencies.

Answer 1

As described in this recipe for the Validator component, validatedBy() returns an alias, not a service directly. This allows you to configure your own Validator service in the DIC:

services:
validator.unique.your_validator_name:
    class: Fully\Qualified\Validator\Class\Name
    tags:
        - { name: validator.constraint_validator, alias: doctrine.orm.validator.unique }

As this UniqueEntity constraint is part of the bridge, it means you should use it in a Symfony2 context. That’s why you can’t really use it outside of the framework.

But you can change this service value to a class name. Attributes are public: https://github.com/symfony/symfony/blob/master/src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntity.php, and according to the documentation given above, it will work.