Symfony form has ManyToOne field but still requires the __tostring() function - symfony

Question

In a Symfony entity that stores the address information of a client I have made a ManyToOne connection with a entity that contains all countries. So the entity has de following link:
/**
* #var string
*
* #ORM\Column(name="country_code", type="string", length=2)
*
* #ORM\ManyToOne(targetEntity="Country")
* #ORM\JoinColumn(name="country_code", referencedColumnName="country_code")
*/
private $countryCode;
In the form generated of this entity I have defined it like this:
->add('countryCode', 'entity', array(
'class' => 'MyBundle:Country',
'choice_label' => 'name_en',
'choice_value' => 'country_code',
'data' => 'nl',
))
So it does not store the primary key but the country_code a two letter code like "nl" for the Netherlands.
Then I have to add __tostring() code to make it work, but why is that? I though the __tostring function would not be required anymore as there is already a ManyToOne connection.
public function __toString()
{
return strval($this->countryCode);
}

Answer 1

First in your entity you just have to write this :
/**
* #ORM\ManyToOne(targetEntity="PathTo/YourBundle/Entity/Country")
*/
private $country;
Then $country will be a reference to a Country Entity (it's ID in the DB),
and will allow you to acces ALL IT'S FIELDS.
After that in your form you should not use
->add('country', 'entity', array(....
As this syntax is deprecated and use instead :
use Symfony\Bridge\Doctrine\Form\Type\EntityType; //don't forget it on top of your form file
->add('country', EntityType::class, array(....
As you probably want to order your countries by alphabetical order you will use a query to do so and eventually your code may look like :
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Doctrine\ORM\EntityRepository;
...
->add('country', EntityType::class, array(
'class' => 'MyBundle:Country',
'query_builder' => function (EntityRepository $er) {
return $er->createQueryBuilder('c')
->orderBy('c.name_en', 'ASC');
},
'choice_label' => 'name_en',
'data' => 'nl'
))
you normally don't have to worry about choice_value, which will be the unique ID of the chosen country : when you'll acces your Client Entity, you will do :
$client->getCountry()->getCountryCode() ;
to get the country code.

Answer 2

I guess you are missing something about how database stores the relationships.
The first problem: you don't need this:
#ORM\Column(name="country_code", type="string", length=2)
... Because #ORM\ManyToOne already describes the schema for this property.
And here we meet the second problem: #ORM\ManyToOne creates an integer column, which contains an ID of the appropriate Country entity. Which means, when you create a form field for this property, it doesn't know which property should it render as a string representation, because your address book (or whatever you called it) entity stores only digits, not the country code.