     /// - `context` : optional MOC.  If nothing is passed, mainContext is assumed.
     /// - `completion` : optional completion block. Called on the main queue.
     
-    public func saveToDisk(context: NSManagedObjectContext? = nil, completion: ErrorCompletionBlock? = nil) {
+    public func saveToDisk(context: NSManagedObjectContext? = nil, completion: ((error: ErrorType?) -> Void)? = nil) {
         guard deletedStore else {
             completion?(error: CoreDataStackError.DeletedStore)
             return

extension CoreDataStack {
    
    //Convenience for dispatching back on the main queue
    private func onMain(withError error: ErrorType? = nil, call completion: ErrorCompletionBlock?)  {
        dispatch_async(dispatch_get_main_queue()) {
            completion?(error: error)
        }

            }
        }
    }
    ///The main context. a NSManagedObjectContext that is created with the MainQueueConcurrencyType concurrencyType.
    public let mainContext: NSManagedObjectContext
    
