From https://twitter.com/jessyMeow/status/652488803874119680

coredata.swift

// This should all be on the MOC, not the class. 
// A singleton MOC like "CoreDataStack" completely blows up CoreData concurrency.
// You need a separate MOC per queue. So you have to work with the right MOC, not a global one.
// (I'm assuming here that CoreDataStack returns a singleton; maybe it makes a new one magically;
// either way, you should work through the moc so that you have a consistent view of the store.)
// Built on the MOC, this is easy, and matches stuff we've done in ObjC for years.
extension NSManagedObjectContext {
    func newInstanceOf<T: NSManagedObject>(type: T.Type) -> T {
        return NSEntityDescription.insertNewObjectForEntityForName(NSStringFromClass(T), inManagedObjectContext: self) as! T
    }

    func allInstancesOf<T: NSManagedObject>(type: T.Type) -> [T] {
        let fetchRequest = NSFetchRequest(entityName: NSStringFromClass(T))
        fetchRequest.entity = NSEntityDescription.entityForName(NSStringFromClass(T), inManagedObjectContext: self)
        return try! self.executeFetchRequest(fetchRequest) as! [T]
    }

    func findInstance<T: NSManagedObject>(predicate: T -> Bool) -> T? {
        return allInstancesOf(T).lazy.filter(predicate).first
    }
}

let moc = CoreDataStack.managedObjectContext

let obj = moc.newInstanceOf(MyObject) // type == MyObject
let all = moc.allInstancesOf(MyObject) // type == [MyObject]

let f = moc.findInstance{ (obj: MyObject) in obj.name == "" } // type == MyObject?
let g: MyObject? = moc.findInstance{ $0.name == "" } // Or be explicit so we can use $0