Incompatible with presence validation on associated record about machinist HOT 3 CLOSED

This is the way ActiveRecord works. You'll get the same error if you do this:

post = Post.new
comment = Comment.new(:post => post)
comment.save

ActiveRecord isn't smart enough to save the post, and set the post_id on the comment.

If you've got a way around this, let me know!

from machinist.

Ran into this myself. The fix is to use validates :post, presence: true instead of using :post_id. This doesn't require the post object to be saved (aka have an id)

While I was at it, I added the validates_associated :post validation too, which causes valid? to be false if the associated post.valid? is also false.

from machinist.

Thank you @rgould!

from machinist.