import UIKit

@UIApplicationMain

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

        // Override point for customization after application launch.

        self.window!.backgroundColor = UIColor.whiteColor()

        self.window!.rootViewController = RootViewController()

        self.window!.makeKeyAndVisible()

        return true

    }

}

import UIKit

class RootViewController: UIViewController {

    override func viewDidLoad() {

        super.viewDidLoad()

        //调用processData函数

        processData { () -> () in

            print("被回调了");

        }

    }

    func processData(printSomething:()->()){

        print("执行操作");

        //执行闭包回调

        printSomething();

    }

}