Subform Validation

AmountModel.php

<?php

namespace Asso\BookBundle\Form;

use Symfony\Component\Validator\Constraints as Assert;
use Symfony\Component\Validator\ExecutionContext;

/**
 * @Annotation
 */
class AmountModel
{
    /**
     * @Assert\Min(99)
     */
    private $debit;

    /**
     * @Assert\Min(99)
     */
    private $credit;


    public function setDebit($debit)
    {
        $this->debit = $debit;
    }
    public function getDebit()
    {
        return $this->debit;
    }

    public function setCredit($credit)
    {
        $this->credit = $credit;
    }
    public function getCredit()
    {
        return $this->credit;
    }

    /**
     * @Assert\True(message = "The amount is invalid")
     */
    public function isCreditValid()
    {
        exit('I am triggered !'); // just to see if the validator goes through this method
        return false;
    }
}

AmountTransformer.php

<?php

namespace Asso\BookBundle\Form;

class AmountTransformer implements DataTransformerInterface
{
    public function transform($value)
    {
        $amount = new AmountModel;

        if( $value < 0 )
        {
            $amount->setDebit(-$value);
            $amount->setCredit(0);
        }
        else
        {
            $amount->setCredit($value);
            $amount->setDebit(0);
        }

        return $amount;
    }

    public function reverseTransform($value)
    {
        if( $value->getCredit() != 0 AND $value->getDebit() != 0 )
        {
            throw new TransformationFailedException('Transformation failed cause amount is not valid');
        }

        return ( $value->getCredit() - $value->getDebit() );
    }
}

AmountType.php

<?php

namespace Asso\BookBundle\Form;

class AmountType extends AbstractType
{
    /**
     * @see Symfony\Component\Form.AbstractType::buildForm()
     */
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('debit', 'integer', array('required' => false))
            ->add('credit', 'integer', array('required' => false));

        $builder->appendClientTransformer(new AmountTransformer);

        return parent::buildForm($builder, $options);
    }

    /**
     * @see Symfony\Component\Form.AbstractType::getDefaultOptions()
     */
    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'Asso\BookBundle\Form\AmountModel',
        );
    }

    /**
     * @see Symfony\Component\Form.AbstractType::getName()
     */
    public function getName()
    {
        return 'asso_book.amount';
    }
}

EntryType.php

<?php

namespace Asso\BookBundle\Form;

class EntryType extends AbstractType
{
    /**
     * @see Symfony\Component\Form.AbstractType::buildForm()
     */
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('label')
            ->add('amount', new AmountType)
            ->add('date')
            ;
    }

    /**
     * @see Symfony\Component\Form.AbstractType::getDefaultOptions()
     */
    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'Asso\BookBundle\Entity\Entry',
        );
    }
}