I have a gridfield in SectionPage managing a has_many dataobject 'Sections' => 'Section', which in turn has_many 'Gallery' => 'GalleryItem' which has_one image.

How can I get the Gridfield to return a thumbnail of the first GalleryItem?

I have tried many variations in Section.php, but feel this is the closest I have got:

public function getThumbnail() {
return $this->Gallery()->First()->Photo()->CMSThumbnail();
}

This gives me a 'Call to a member function Photo() on a non-object in...' error.

Can anyone give me some help with this problem?

Make sure $this->Gallery()->First() is returning an object and not just a VIewableData array. I know I've run into this in the past

It may alos work to create a getThumbnial on GalleryItem and set it as virtual property