NSCondition

@UIApplicationMain

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    var product = [String]()

    let condition = NSCondition()

    

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

        // Override point for customization after application launch.

        

        NSThread.detachNewThreadSelector("consume", toTarget: self, withObject: nil)

        NSThread.detachNewThreadSelector("create", toTarget: self, withObject: nil)

        

        return true

    }

    

    func create() {

        condition.lock()

        print("create a product")

        product.append("*")

        condition.signal()

        condition.unlock()

    }

    

    func consume() {

        condition.lock()

        while product.count == 0 {

            print("waiting for create product")

            condition.wait()

        }

        print("consume a product")

        product.removeFirst()

        condition.unlock()

    }

}