Question

我正在进行在线斯坦福IOS开发课程，我遇到了一个我不知道如何处理的错误。当我切换到拆分视图控制器中的详细视图时，我能够将详细信息UIView的参数从出口的didSet中的详细信息UIViewController设置到视图。稍后，当我尝试从控制器访问或改变详细视图时，即使视图仍在屏幕上并响应手势，视图变量（出口）也为零。这是拆分视图控制器中主视图的准备方法

Map<Key, List<Value>>

这是详细视图控制器。我评论了有趣的部分。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {  
    let destinationViewController = segue.destination  
    if let graphViewController = destinationViewController as? GraphViewController {  
        if let identifier = segue.identifier{  
            switch identifier {  
            case "DisplayGraph":  
                graphViewController.function = funcForGraphView(_:)  
            default:  
                break  
            }  
        }  
    }  
}

这是详细视图中的相关变量

class GraphViewController: UIViewController {  
@IBOutlet weak var graphView: GraphView!{  
    didSet{  
        graphView.addGestureRecognizer(UITapGestureRecognizer(target: graphView, action: #selector(graphView.tap(recognizer:))))  
        graphView.addGestureRecognizer(UIPanGestureRecognizer(target: graphView, action: #selector(graphView.pan(recognizer:))))  
        graphView.addGestureRecognizer(UIPinchGestureRecognizer(target: graphView, action: #selector(graphView.zoom(recognizer:))))  
        graphView.function = cos //I can set variables in the view here  
        // After this didSet I am no longer able to set or read any variables from the graphView  
    }  
}  
var function: ((Double)->(Double))? {  
    didSet{  
        if let newfunction = function {  
            graphView.function = newfunction // I can not set or access variables in the view here since for some reason graphView is nil  
        }  
    }  
}

Storyboard Picture 任何帮助将不胜感激，希望这不是一个愚蠢的问题。如果有更多信息有用，请告诉我。谢谢！

Answer 1

由于你的视图没有完全加载，因为你的推视控制它将是零。所以你需要传递如下：

在GraphViewController中

var yourValue : ((Double)->(Double))?

override func viewDidLoad() {
        super.viewDidLoad()
         self.function = yourValue
}

导航时设置值

 if let identifier = segue.identifier{  
            switch identifier {  
            case "DisplayGraph":  
                graphViewController.yourValue = funcForGraphView(_:)  
            default:  
                break  
            }  
        }

在segue之后查看出口零

1 个答案: