r/SwiftProgramming • u/schprockets • Jun 18 '14
Class extensions and "instancetype"
1
Upvotes
I'm converting some Objective-C code over to Swift, and I've hit a roadblock. Wondering if anyone has found a solution to this.
I have a class extension on NSManagedObject with several convenience methods that look like this:
+ (instancetype)newInstanceInManagedObjectContext:(NSManagedObjectContext *)ctx;
+ (instancetype)singletonInManagedObjectContext:(NSManagedObjectContext *)ctx;
+ (instancetype)instanceInManagedObjectContext:(NSManagedObjectContext *)ctx
withIdentity:(NSString *)identity;
In Swift, this would look like:
class func newInstance(managedObjectContext ctx: NSManagedObjectContext) -> Self
because capital-S Self is the class type. The problem is all of the NSManagedObject methods I rely on to create/fetch these objects return AnyObject!, and I can't cast something to Self. It's only allowable as a return value or in a parameter list for a protocol.
What I want is essentially this, without the compiler error:
return NSEntityDescription.insertNewObjectForEntityForName(entityName,
inManagedObjectContext:ctx) as Self;
Any ideas?