Xcode 12 中的 Switch 必须详尽无遗

Posted 2023-03-15

【中文标题】Xcode 12 中的 Switch 必须详尽无遗

【英文标题】：Switch must be exhaustive in Xcode 12

【发布时间】：2020-09-17 04:56:27

【问题描述】：

在新的 Xcode 12 中，我在权限范围内遇到了一个特殊错误。 开关必须详尽，添加 .limited 大小写。 虽然我添加了 .limited 大小写，但它仍然显示此错误。我在使用开关盒的地方得到这个。你能为我指出正确的方向吗。我最近将我的项目从 Xcode 11 升级到 Xcode 12，所以在这里有点困惑。

func openPhotoController(item: InfoItem) 
    
    
    let status = phphotoLibrary.authorizationStatus()
    
    switch status 
    case .authorized:
        
        DispatchQueue.main.async
        
            let photoLib = photoLibViewController()
            photoLib.delegate = self
            photoLibCropImage = false
            photoLib.modalTransitionStyle = .crossDissolve
            photoLib.modalPresentationStyle = .fullScreen
            photoLib.allowMultipleSelection = false
            self.present(photoLib, animated: true, completion: nil)
        
        print("authorized")
    //handle authorized status
    case .denied, .restricted :
        
        print("denied")
        
        AlertManager.showAlertView(title: "Alert?", subtitle: "Please allow access to your photo library to use this functionality", showCancelButton: true, okButtonTitle: "Go to Settings", cancelButtonTitle: "Cancel") 
            
            if let url = URL(string:UIApplication.openSettingsURLString)
            
                if UIApplication.shared.canOpenURL(url)
                
                    UIApplication.shared.open(url, options: [:], completionHandler: nil)
                
            
        
    //handle denied status
    case .notDetermined:
        // ask for permissions
        PHPhotoLibrary.requestAuthorization  status in
            switch status 
            case .authorized:
                
                print("authorized")
                
                DispatchQueue.main.async
                
                    let photoLib = photoLibViewController()
                    photoLib.delegate = self
                    photoLibCropImage = false
                    photoLib.modalTransitionStyle = .crossDissolve
                    photoLib.modalPresentationStyle = .fullScreen
                    photoLib.allowMultipleSelection = false
                    self.present(photoLib, animated: true, completion: nil)
                
            // as above
            case .denied, .restricted:
                
                print("denied")
            // as above
            case .notDetermined:
                print("notDetermined")
            // won't happen but still
            case .limited:
                print("notDetermined")
            default:
                print("notDetermined")
              
        
    

【问题讨论】：

有2个开关。外部开关（父开关）没有'case .limited'。

thanks 有点惊慌，忘记了基础

【参考方案1】：

在 WWDC 2020 中，iOS 14 Apple 推出了一项新功能，该功能将限制对照片库的访问。您缺少外部主开关的 .limited 外壳。您更新的代码：

switch PHPhotoLibrary.authorizationStatus(for: .readWrite) 
case .notDetermined:
    // ask for access
case .restricted, .denied:
    // sorry
case .authorized:
    // we have full access
 
// new option: 
case .limited:
    // we only got access to a part of the library

更多，可以查看here

【参考方案2】：

为外部开关添加.limited case。

如果你不想处理它，你总是可以插入一个默认情况（你有你的内部开关，但没有外部开关）：

...
default:
    // Otherwise, do something else

关于 Swift 开关的文档：https://docs.swift.org/swift-book/LanguageGuide/ControlFlow.html.