斯威夫特3-准备塞古 [英] Swift 3 - Prepare Segue

问题描述

我的故事板上有3个场景.我最初的View Controller是导航控制器，然后是根视图控制器与UI ViewController(视图控制器a)的关系，然后我将按钮从ViewController中的按钮推到了第三个ViewController(视图控制器b)中场景.我给了推送搜索一个标识符.现在，我正在尝试像下面这样在第二个视图控制器(视图控制器a)中准备segue:

I have 3 scenes in my storyboard. My initial View Controller is a Navigation Controller, then there is a relationship root view controller to a UI ViewController (view controller a) and then I have a push segue from a button in the ViewController to the third ViewController (view controller b) in the scene. I have given the push segue an identifier. Now I am trying to prepare my segue in the 2nd view controller (view controller a) like so:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "HistorySegue" {
            if let viewController = segue.destination as? HistoryController {
                viewController.detailItem = barcodeInt as AnyObject
            }
        }
    }

但是，当我运行此代码并按下控制器a中的按钮时，出现以下错误:

However when I run this code and push the button in controller a I get the following error:

致命错误:尝试桥接一个包含nil的隐式展开的可选

fatal error: attempt to bridge an implicitly unwrapped optional containing nil

我做错了什么?

推荐答案

用以下代码替换代码，至少不会崩溃.

Replace your code with the following, it will not crash at least.

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "HistorySegue" {
            if let viewController = segue.destination as? HistoryController {
              if(barcodeInt != nil){
                viewController.detailItem = barcodeInt as AnyObject
               }
            }
        }
    }

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