Strongly-typed Core Data ideas

Managed.swift

import CoreData

/// Designed to add functionality to classes deriving from *NSManagedObject*
protocol Managed {}

// This keeps us from having to explicitly implement Managed
// on all NSManagedObject subclasses.
extension NSManagedObject: Managed {}

// Managed is extended instead of NSManagedObject,
// so that we can work with derived types, and avoid casting externally.
extension Managed where Self: NSManagedObject {
  static var newManagedObject: Self {
      return NSEntityDescription.insertNewObjectForEntityForName(className,
         inManagedObjectContext: CoreDataStack.managedObjectContext
      ) as! Self
   }
   
   static var storedInContext: [Self] {
      let fetchRequest = NSFetchRequest(entityName: className)
      fetchRequest.entity = NSEntityDescription.entityForName(className,
         inManagedObjectContext: CoreDataStack.managedObjectContext
      )!
      return try! CoreDataStack.managedObjectContext.executeFetchRequest(fetchRequest)
         as! [Self]
   }
}

// Keep this in another file.
public extension NSObject {
    public static var className: String {
        return NSStringFromClass(self).componentsSeparatedByString(".").last!
    }
}