get iCloud User ID

getICloudUserID.swift

import CloudKit

/// async gets iCloud record ID object of logged-in iCloud user
func iCloudUserIDAsync(complete: (instance: CKRecordID?, error: NSError?) -> ()) {
    let container = CKContainer.defaultContainer()
    container.fetchUserRecordIDWithCompletionHandler() {
        recordID, error in
        if error != nil {
            print(error!.localizedDescription)
            complete(instance: nil, error: error)
        } else {
            print("fetched ID \(recordID?.recordName)")
            complete(instance: recordID, error: nil)
        }
    }
}

container.fetchUserRecordIDWithCompletionHandler() { ... } should probably be container.fetchUserRecordIDWithCompletionHandler({ ... })