OMG @hube2 – brilliant.
Just using _thumbnail_id for the field name is so easy and makes everything work perfectly. You should pin this at the top of the thread.
Using the filter method and a custom field name:
- Works great on first save
- Removing the image from ACF field does not remove the image as the featured image (without adding some extra code to handle this)
- If a featured image exists already it doesn’t auto populate into the ACF field
- If a featured image exists already you can add an image to the ACF field and successfully get them to be different
Just using _thumbnail_id for the field name makes all of the above scenarios work perfectly.
