Using your nose / face example for a one-to-one relationship, I created two classes:
What I expected to happen is when creating a Face object and assign a Nose object to it, both will be saved:
This isn't working, but this is:
And this (what I really don't understand):
I don't understand, why (3) works as expected, (1) is not. It seems, that because of the bidirectional one-to-one relation the nose object isn't valid (nose.validate() => false), because in (1) I did not assign the face to the nose object, as in (2), but in (3) this is done automatically.