let queue = dispatch_get_global_queue(QOS_CLASS_BACKGROUND, 0)
    let group = dispatch_group_create()

    dispatch_group_async(group, queue) {
      print("Job 1 done")
    }

    dispatch_group_async(group, queue) {
      print("Job 2 done")
    }

//    OR
//    let block1 = NSBlockOperation {
//      print("Job 1 done")
//    }
//
//    let block2 = NSBlockOperation {
//      print("Job 2 done")
//    }
//
//    for operation in [block1, block2] {
//      dispatch_group_async(group, queue, {
//        operation.start()
//      })
//    }

    dispatch_group_notify(group, dispatch_get_main_queue()) {
      print("All done")
    }