Library and Book. On my Library create page I can select the books that belong to this library. When I save the library, the books are also saved in the relationship table.LibraryObserver so that I can perform some processing when it is created - however, the processing involves the books too.public function created(Library $library) method of my LibraryObserver the relationship doesn't exist yet (presumably because it hasn't been saved at this point - because we're firing on the Library created event).