关于ios：在两个ViewControllers（委托）之间传递数据 – Swift

Passing data between two ViewControllers (delegate) - Swift

本问题已经有最佳答案，请猛点这里访问。

我有两个ViewController's.。

FirstVC-I具有EDOCX1，2，EDCX1，3，与SeGuE"MODE"

SecondVC—我有PickerView和button(回到firstvc)：

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

我在SecondViewController中创建了一个代表：

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protocol SendDataDelegate {
func sendData(text:String)
}

下一步：

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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
}

我在PickerView中的职能，在此职能中，我将我的代表用作：

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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：

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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
}
}

请帮我解决这个问题。