Following the steps along to create a custom mapping model, ending at page 157, results in:
2018-12-25 12:23:38.483789-0500 UnCloudNotes[71393:1048312] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unacceptable type of value for to-many relationship: property = "attachments"; desired type = NSSet; given type = NSManagedObject; value = <NSManagedObject: 0x600003ea3070> (entity: Note; id: 0xa2129dc2c43dc805 <x-coredata://65151617-DA34-4A81-AE4B-2AA175760A4B/Note/p1> ; data: {
attachments = (
"0xa2129dc2c43dc805 <x-coredata://65151617-DA34-4A81-AE4B-2AA175760A4B/Note/p1>"
);
body = "Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamc";
dateCreated = "2018-12-25 17:03:23 +0000";
displayIndex = 0;
title = "Another title";
}).'
I understand what it’s saying but don’t know how to fix it via mapping model file… that’s why I bought the book…