class func uuid(completionHandler: @escaping (String) -> ()) {
    if let uuid = UIDevice.current.identifierForVendor?.uuidString {
        completionHandler(uuid)
    }
    else {
        // If the value is nil, wait and get the value again later. This happens, for example, after the device has been restarted but before the user has unlocked the device.
        // https://developer.apple.com/documentation/uikit/uidevice/1620059-identifierforvendor?language=objc
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
            uuid(completionHandler: completionHandler)
        }
    }
}

斯威夫特2.2

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

    let userDefaults = NSUserDefaults.standardUserDefaults()

    if userDefaults.objectForKey("ApplicationIdentifier") == nil {
        let UUID = NSUUID().UUIDString
        userDefaults.setObject(UUID, forKey: "ApplicationIdentifier")
        userDefaults.synchronize()
    }
    return true
}

//Retrieve
print(NSUserDefaults.standardUserDefaults().valueForKey("ApplicationIdentifier")!)

在swift 4,5 您可以使用下面的代码获取UUID。

print(UIDevice.current.identifierForVendor!.uuidString)

输出

除此之外，您可以从连接的设备获得多个属性。

 UIDevice.current.name             // e.g. "My iPhone"
 UIDevice.current.model            // e.g. @"iPhone", @"iPod touch"
 UIDevice.current.localizedModel   // localized version of model
 UIDevice.current.systemName       // e.g. @"iOS"
 UIDevice.current.systemVersion    // e.g. @"15.5"

if (UIDevice.current.identifierForVendor?.uuidString) != nil
        {
            self.lblDeviceIdValue.text = UIDevice.current.identifierForVendor?.uuidString
        }

从iOS 11开始，你可以使用苹果的api: DeviceCheck

class func uuid(completionHandler: @escaping (String) -> ()) {
    if let uuid = UIDevice.current.identifierForVendor?.uuidString {
        completionHandler(uuid)
    }
    else {
        // If the value is nil, wait and get the value again later. This happens, for example, after the device has been restarted but before the user has unlocked the device.
        // https://developer.apple.com/documentation/uikit/uidevice/1620059-identifierforvendor?language=objc
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
            uuid(completionHandler: completionHandler)
        }
    }
}