Swift core data

Question

What is the reason of this problem (cant map from one to many core data )??

Answer 1

https://stackoverflow.com/questions/24329322/cant-access-one-to-many-relationships-in-coredata-using-swift

"...trying to iterate over a collection, but instead getting an instance...your relationship [may be] set up as 'to one' in the data modeler...[set it to 'to many'].
...select the relationship...in Data Model Inspector examine "type", which is set to 'to one' by default. "

I don't know a thing about the language. Hope it helps.