Ios 将一个变量从一个viewcontroller传递到另一个viewcontroller

我不熟悉swift语言，知道这个问题是重复的。我发现了几个类似的问题和答案，但我无法解决这个问题

我想将detectionString变量的值从ScanViewController传递给ResultViewController

ScanViewcontroller如下所示：

import UIkit

class ScanViewController: UIViewController  {

    var detectionString : String!

    override func viewDidLoad() {
        super.viewDidLoad()

        detectionString = “SomeDetectedString”
    }

    override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
        if (segue.identifier == "MySegue") {
            var svc = segue.destinationViewController as ResultViewController;
            svc.detectedString = detectionString
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

import UIkit

class ResultViewController: UIViewController {

    var detectedString: String!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor=UIColor.whiteColor()
        println(detectedString)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

结果视图控制器如下所示：

import UIkit

class ScanViewController: UIViewController  {

    var detectionString : String!

    override func viewDidLoad() {
        super.viewDidLoad()

        detectionString = “SomeDetectedString”
    }

    override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
        if (segue.identifier == "MySegue") {
            var svc = segue.destinationViewController as ResultViewController;
            svc.detectedString = detectionString
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

import UIkit

class ResultViewController: UIViewController {

    var detectedString: String!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor=UIColor.whiteColor()
        println(detectedString)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

---

println（detectedString）没有给出任何结果。问题是如何从ScanViewController中获取变量？

您的

segue.identifier==“MySegue”

是一种如何不以应有的方式进行比较的方法

用下面的函数替换代码，就完成了

override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {
    let segueName: String = segue.identifier!;
    if (segueName == "MySegue") {
        var svc = segue.destinationViewController as DetailVC;
        svc.detectedString = detectionString
    }
}

---

您有三个选择：

使用

prepareforsgue

方法获取目标ViewController并设置属性

设置两个ViewController之间的代理关系以进行通信

使用NSNotificationCenter设置观察者

---

这听起来可能很奇怪，但代码没有问题，但它不能正常工作。我使用了相同的代码，它忽略了segue。然后我将

ScanViewController

嵌入到故事板中的导航控制器中。我还调用了

ScanViewController viewDidLoad

中的

self.performsguewithidentifier（“MySegue”，sender:self）

来启动segue。然后一切都像一个符咒。你的准备工作很好。Yuvrajsinh的建议很好，但没有必要（我在将DetailVC更改为ResultViewController后尝试过）。没有导航控制器，一切都无法工作

segue.identifier

是一个字符串，它将用于直接的Swift字符串比较

以下是ScanViewController的代码：

import UIkit

class ScanViewController: UIViewController  {

    var detectionString : String!

    override func viewDidLoad() {
        super.viewDidLoad()


        detectionString = "SomeDetectedString"
        println(detectionString)
        self.performSegueWithIdentifier("MySegue", sender: self)
    }

    override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {

        if (segue.identifier == "MySegue" || segue.identifier == "SegueFromButton") {
            println("prepareForSegue")
            var svc = segue.destinationViewController as ResultViewController;
            svc.detectedString = detectionString
            println("svc.detectedString: \(svc.detectedString)")
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


}

import UIkit

class ResultViewController: UIViewController {

    var detectedString: String!

    override func viewDidLoad() {
        println("Result Load View")
        super.viewDidLoad()
        self.view.backgroundColor=UIColor.whiteColor()
        println("detectedString in Result: \(detectedString)")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

对于ResultViewController：

import UIkit

class ScanViewController: UIViewController  {

    var detectionString : String!

    override func viewDidLoad() {
        super.viewDidLoad()


        detectionString = "SomeDetectedString"
        println(detectionString)
        self.performSegueWithIdentifier("MySegue", sender: self)
    }

    override func prepareForSegue(segue: UIStoryboardSegue,sender: AnyObject!) {

        if (segue.identifier == "MySegue" || segue.identifier == "SegueFromButton") {
            println("prepareForSegue")
            var svc = segue.destinationViewController as ResultViewController;
            svc.detectedString = detectionString
            println("svc.detectedString: \(svc.detectedString)")
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }


}

import UIkit

class ResultViewController: UIViewController {

    var detectedString: String!

    override func viewDidLoad() {
        println("Result Load View")
        super.viewDidLoad()
        self.view.backgroundColor=UIColor.whiteColor()
        println("detectedString in Result: \(detectedString)")
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

---

可能重复感谢您的回答，如果我通过@BIAction触发segue，我可以从第一个值中获得值

@IBAction func showssecond（发送者：AnyObject）{self.performsguewithidentifier（“MySegue”，发送者：nil）}

每当我试图以编程方式触发segue时，它就会崩溃。感谢您的回答，非常感谢您的帮助，它按照您描述的方式工作。除此之外，我还尝试使用appdelegate获取变量的访问值。再次感谢。谢谢，我试过了，它对我也很有效。