Add error to Symfony 2 form element

I check some validation in my controller. And I want to add error to specific element of my form on failure. My form:

use Symfony\Component\Form\FormError;

// ...

$config = new Config();
$form = $this->createFormBuilder($config)
        ->add('googleMapKey', 'text', array('label' => 'Google Map key'))
        ->add('locationRadius', 'text', array('label' => 'Location radius (km)'))
        ->getForm();

// ...

$form->addError(new FormError('error message'));

addError() method adds error to form, not to element. How can I add an error to locationRadius element?

You can do

$form->get('locationRadius')->addError(new FormError('error message'));

As form elements are also of FormInterface type.

OK guys, I have another way. It is more complex and only for specific cases.

My case:

I have a form and after submit I post data to the API server. And errors I got from the API server as well.

API server error format is:

array(
    'message' => 'Invalid postal code',
    'propertyPath' => 'businessAdress.postalCode',
)

My goal is to get flexible solution. Lets set the error for the corresponding field.

$vm = new ViolationMapper();

// Format should be: children[businessAddress].children[postalCode]
$error['propertyPath'] = 'children['. str_replace('.', '].children[', $error['propertyPath']) .']';

// Convert error to violation.
$constraint = new ConstraintViolation(
    $error['message'], $error['message'], array(), '', $error['propertyPath'], null
);

$vm->mapViolation($constraint, $form);

That's it!

NOTE! addError() method bypasses [error_mapping][1] option.

---

My form (Address form embedded in the Company form):

Company

<?php

namespace Acme\DemoBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Validator\Constraints;

class Company extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('companyName', 'text',
                array(
                    'label' => 'Company name',
                    'constraints' => array(
                        new Constraints\NotBlank()
                    ),
                )
            )
            ->add('businessAddress', new Address(),
                array(
                    'label' => 'Business address',
                )
            )
            ->add('update', 'submit', array(
                    'label' => 'Update',
                )
            )
        ;
    }

    public function getName()
    {
        return null;
    }
}

Address

<?php

namespace Acme\DemoBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Validator\Constraints;

class Address extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            // ...
            ->add('postalCode', 'text',
                array(
                    'label' => 'Postal code',
                    'constraints' => array(
                        new Constraints\NotBlank()
                    ),
                )
            )
            ->add('town', 'text',
                array(
                    'label' => 'Town',
                    'constraints' => array(
                        new Constraints\NotBlank()
                    ),
                )
            )
            ->add('country', 'choice',
                array(
                    'label' => 'Country',
                    'choices' => $this->getCountries(),
                    'empty_value' => 'Select...',
                    'constraints' => array(
                        new Constraints\NotBlank()
                    ),
                )
            )
        ;
    }

    public function getName()
    {
        return null;
    }
}

[1]: http://symfony.com/doc/current/reference/forms/types/form.html#error-mapping "error_mapping"