Writing custom Validators
=========================

File validations in the OneupUploaderBundle were made using the [EventDispatcher](http://symfony.com/doc/current/components/event_dispatcher/introduction.html) component.
If you want to enhance file validations in your application, you can register your own `EventListener` like in the example below.
To fail a validation, throw a `ValidationException`. This will be catched up by the `Controller`.

```php
namespace Acme\DemoBundle\EventListener;

use Oneup\UploaderBundle\Event\ValidationEvent;
use Oneup\UploaderBundle\Uploader\Exception\ValidationException;

class AlwaysFalseValidationListener
{
    public function onValidate(ValidationEvent $event)
    {
        $config  = $event->getConfig();
        $file    = $event->getFile();
        $type    = $event->getType();
        $request = $event->getRequest();

        // do some validations
        throw new ValidationException('Sorry! Always false.');
    }
}
```

After that register your new `EventListener` in the `services.yaml` of your application.

```yml
services:
    acme_demo.always_false_listener:
        class: Acme\DemoBundle\EventListener\AlwaysFalseValidationListener
        tags:
            - { name: kernel.event_listener, event: oneup_uploader.validation, method: onValidate }
```

Since version 1.6 you can listen to an event thrown for every uploader specifically. The name for the event is `oneup_uploader.validation.{type}` where `{type}` represents the config key of the uploader you want to target.