adding location hidden field in Calendar formType

src/Bundle/ChillCalendarBundle/Form/CalendarType.php

@@ -2,6 +2,7 @@
 
 namespace Chill\CalendarBundle\Form;
 
+use Chill\MainBundle\Entity\Location;
 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\OptionsResolver\OptionsResolver;
@@ -155,7 +156,7 @@ class CalendarType extends AbstractType
                 }
             ))
         ;
-    
+
         $builder->add('calendarRange', HiddenType::class);
         $builder->get('calendarRange')
             ->addModelTransformer(new CallbackTransformer(
@@ -178,6 +179,20 @@ class CalendarType extends AbstractType
             ))
         ;
 
+        $builder->add('location', HiddenType::class)
+            ->get('location')
+            ->addModelTransformer(new CallbackTransformer(
+                function (?Location $location): string {
+                    if (null === $location) {
+                        return '';
+                    }
+                    return $location->getId();
+                },
+                function (?string $id): Location {
+                    return $this->om->getRepository(Location::class)->findOneBy(['id' => (int) $id]);
+                }
+            ))
+        ;
 
     //     $builder->add('invites', HiddenType::class);
     //     $builder->get('invites')