Error "Impossible to invoke a method ("id") on a null variable" when loading ManyToOne with sonata_type_model_list through sonata_type_admin

[nrodr...@tupaca.com]

Hi all,

I've a problem when trying to load a sonata_type_model_list field within a sonata_type_admin. It gives me the following error:

Impossible to invoke a method ("id") on a null variable in SonataDoctrineORMAdminBundle:Form:form_admin_fields.html.twig at line 60

My entities:

• AppBundle\Entity\Page - it have a OneToOne to Content
  
• AppBundle\Entity\Content\Content (abstract)
  
• AppBundle\Entity\Content\ContentText extends Content
  
• AppBundle\Entity\Content\ContentImage extends Content - it have a ManyToOne to media-bundle's "Media"
  
• AppBundle\Entity\Content\ContentVideo extends Content - it have a ManyToOne to media-bundle's "Media"

My admin classes:

• AppBundle\Admin\PageAdmin - for AppBundle\Entity\Page

• AppBundle\Admin\ContentAdmin - for AppBundle\Entity\Content\Content -  from configureFormFields it loads the needed fields for each "Content" subclass (text for text, and sonata_type_model_list for medias)
  

Details of the error:

From ContentAdmin

Everything works fine, and I'm able to edit everything, using sonata_type_model_list

From PageAdmin

When I load the related (OneToOne) Content using sonata_type_admin:

• if the content related is a ContentText , it works fine. (Actually, I've more Content subclasses similar to ContentText, and it works fine. But none of them have ManyToOne fields)
  
• If the content related is a ContentImage or ContentVideo (both loaded with sonata_type_model_list), it fires the error:

Impossible to invoke a method ("id") on a null variable in SonataDoctrineORMAdminBundle:Form:form_admin_fields.html.twig at line 60

My versions:

• sonata-project/admin-bundle 2.3.10
  
• sonata-project/doctrine-orm-admin-bundle 2.3.4
  
• sonata-project/media-bundle 2.3.4

I've read similar errors on github, but I'm not sure if they are related. Just for your info, I copy them:

https://github.com/sonata-project/SonataDoctrineORMAdminBundle/issues/222

https://github.com/sonata-project/SonataDoctrineORMAdminBundle/issues/252

Thanks!!

[nrodr...@tupaca.com]

I've some news:

It seems that the problem occurs only if I use inheritance on Content... If I just use a relation from Page to ContentImage, it works fine.

[nrodr...@tupaca.com]

More data:

The problem just occurs if I load more than one sonata_type_admin per form, and one of them has ManyToOne relation.

[Abhishek Niraula]

I had missed use Doctrine\ORM\Mapping as ORM;
Adding this line in Media entity fixed the issue for me. And my current Entity structure is same as discussed in the previous comment