Question

我在iOS编程方面相当新。我有这个设置：

{p> mapLayer查看IB，课程ViewController

{p> ViewController查看IB，课程SecondController

我有协议：

secondController

我在SecondController上有委托变量：

protocol SecondControllerDelegate {
    func getSomething() -> String
}

现在，根据各处的提示，为了让我可以在class secondController: UIViewController { var delegate: SecondControllerDelegate? @IBOutlet weak var labelStatus: UILabel! override func ViewDidLoad() { super.viewDidLoad() } @IBAction func buttonTouch(sender: AnyObject) { labelStatus.text = delegate?.getSomething() } func try () { labelStatus.text = "testing" } }调用delegate?.getSomething()，我需要在viewController上设置如下：

SecondController.buttonTouch()

但这会产生错误class ViewController: UIViewController, SecondControllerDelegate { override func viewDidLoad () { super.viewDidLoad() SecondController.delegate = self } func doSomething () -> String { return "testing" } }。

其他一些网站说：

'SecondController.type' does not have a member named 'delegate'

有了这个，就没有错误。但是如果我在应该调用委托的第二个屏幕上执行某些操作，它就不会调用委托，就像SecondController是两个不同的对象（一个是由StoryBoard创建的，一个是在ViewController中手动创建的），即class ViewController: UIViewController, SecondControllerDelegate { var secondController = SecondController() override func viewDidLoad () { super.viewDidLoad() secondController.delegate = self } func doSomething () -> String { return "testing" } }应该更改为＆＃34;测试＆＃34;，根本不会发生变化。但是如果调用函数labelStatus，它会改变。我该怎么做？

编辑：我忘了提到我使用了NavigationController，并且从第一个屏幕过渡到第二个屏幕。

Answer 1

因为您尝试学习如何在Swift中构建委托，所以我在下面写了一个简单的委托示例

protocol SecondViewControllerDelegate {
    func didReceiveInformationFromSecondViewcontroller (information: String)
}

class ViewController: UIViewController, SecondViewControllerDelegate {

    func openSecondViewController () {
        if let secondViewControllerInstance: SecondViewController = storyboard?.instantiateViewControllerWithIdentifier("SecondViewController") as? SecondViewController {
            secondViewControllerInstance.delegate = self
            navigationController?.pushViewController(secondViewControllerInstance, animated: true)
        }
    }

    func didReceiveInformationFromSecondViewcontroller(information: String) {
        ////Here you get the information, after sendInfoToViewController() has been executed
    }

}


class SecondViewController: UIViewController {

    var delegate: SecondViewControllerDelegate?

    func sendInfoToViewController () {
        delegate?.didReceiveInformationFromSecondViewcontroller("This ist the information")
    }

}

<强>更新

在使用Storyboard Segues时采用相同的方法

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

将具有屏幕视图的另一个类的委托设置为self

1 个答案: