[SOLVED] What is the right approach to validate multiple checkboxes at once in Symfony2 (one required)?

What is the right approach to validate multiple checkboxes at once in Symfony2 (one required)?

Let's say we have a Symfony2 form containing 3 checkboxes (A, B, C) and we want the user to tick at least one checkbox in order to validate the form, so any combination ([A], [B], [C], [A,B], [A,C], [B,C] ,[A,B,C]) would return true and no selection [] returns false.

What is the right approach to achieve this using Symfony validators on Doctrine objects?

Edit:
Each checkbox is mapped to it's own column in the database using Doctrine @ORM\Column(type="boolean")

Solution

Problem solved.

Based on Symfony2 Class Constraint Validator documentation and on Added info on changes to setting validation subpath to UPGRADE-2.1.md

In my entity class I've added:

class Message
{

  // ...

  // check if user selected at least one network to publish the message
  public function isNetworkSelected(ExecutionContext $context)
  {
    if (!$this->network_twitter && !$this->network_facebook && !$this->network_googleplus)
    {
      $context->addViolationAtSubPath('network_facebook', 'Please select at least one network', array(), null);
    }
  }

  // ...

}

In validation.yml:

MY\MessageBundle\Entity\Message
    constraints:
        - Callback:
            methods:   [isNetworkSelected]