I created a generic CoreDataFetchRequest a while ago and love it. It casts the results to the expected values or throws an error if something went wrong, which it shouldn’t ever, logically – but the Core Data API currently returns AnyObject everywhere, so I have to deal with that.
Swift 2 brings a lot of Cocoa API changes. For one, Core Data’s NSManagedObject’s executeFetchRequest(_:) can throw, returns a non-optional on success, but still returns [AnyObject]. While refactoring existing code to use do-try-catch, I found the optional casting to [MyEntity] cumbersome.
Brent Simmons starts with Swift. And just as I, he struggles with value types, protocols, and generics: once a protocol references another or has a dependency on Self, you cannot use it as a type constraint or placeholder for all descending objects. You either have to use generics to expose a variant for each concrete type, or you re-write the protocol. There’s no equivalent to the way Objective-C did this: something like id<TheProtocol> just doesn’t exist. Swift is stricter. So how do you deal with that?
I used custom collection classes a lot for the Word Counter to let the compiler help me prevent mistakes. Swift generics were a godsend for that kind of safety. Now, Objective-C can achieve similar awesomeness.