在两个ViewControllers（委托）之间传递数据 – Swift

我有两个ViewController's.

1. FirstVC – 我有label和button与segue“模态”

2. SecondVC – 我有PickerView和button （回到FirstVC）：

    @IBAction func bntback(sender: AnyObject) { self.dissmissViewControllerAnimatied(true, completion: nil) } 

我在SecondViewController创build委托为：

 protocol SendDataDelegate { func sendData(text:String) } 

下一个：

 class SecondVC: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate { var delegate: SendDataDelegate! var firstvc = FirstVC() var arr = ["First", "Second", "Third"] @IBOutlet var pickview: UIPickerView! override func viewDidLoad() { super.viewDidLoad() pickview.dataSource = self pickview.selegate = self } 

我的PickerView函数，在这个函数中我使用我的委托：

 func pickerView (pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) { var text = arr[row] dispatch_async(dispatch_get_main_quene(), { self.delegate.sendData(text)//there is an error: "fatal error: unexpectedly found nil while unwrapping an Optional value" )} } 

FirstVC：

 class FirstVC: UIViewController, SendDataDelegate { var data = SecondVC() //.... override func viewDidLoad() { super.viewDidLoad() self.data.delegate = self } func sendData (text:String) { mylable.text = text //or //var txt = text //mylable.text = txt } } 

请帮助我解决这个问题。

Answer 1

1）您需要将委托设置为prepareForSegue：

 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) { if let viewController = segue.destinationViewController as? SecondVC { viewController.delegate = self } } 

更新：

2）将delegate设置为可选

 class SecondVC: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate { var delegate: SendDataDelegate? ... func pickerView (pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) { var text = arr[row] dispatch_async(dispatch_get_main_quene(), { self.delegate?.sendData(text) )} }