Xcode代码报错求助：多个SwiftUI编译错误排查修复

逐个错误排查与修复 #

1. Invalid redeclaration of ContentView #

• 问题：项目中存在重复的ContentView定义，或Xcode缓存导致识别错误。
• 修复：
  • 检查所有.swift文件，删除其他定义ContentView的代码；
  • 执行Xcode清理操作：Cmd + Shift + K清除缓存后重新编译。

2. Instance will be immediately deallocated because property navigationDelegate is weak #

• 问题：WKWebView的navigationDelegate是弱引用，直接创建的WebViewCoordinator没有强引用持有，会被立即释放。
• 修复：在BrowserView中用@State持有WebViewCoordinator实例，确保生命周期匹配：

  struct BrowserView: View {
      @State private var webView = WKWebView()
      @State private var coordinator: WebViewCoordinator?
  
      var body: some View {
          WebView(webView: $webView)
              .onAppear {
                  if let url = URL(string: "https://youtube.com") {
                      webView.load(URLRequest(url: url))
                  }
                  coordinator = WebViewCoordinator()
                  webView.navigationDelegate = coordinator
              }
      }
  }
  

3. weak may only be applied to class and class-bound protocol types, not FilesView #

• 问题：FilesView是SwiftUI值类型（struct），weak仅适用于类类型。
• 修复：将FilesView的状态抽离到ObservableObject类中，让Coordinator持有该类的弱引用：

  class FilesViewModel: ObservableObject {
      @Published var downloadedFiles = [String]()
      @Published var storageTaken: String = ""
  
      func loadFiles() {
          // 原loadFiles逻辑
      }
  }
  
  struct FilesView: View {
      @StateObject private var viewModel = FilesViewModel()
  
      var body: some View {
          VStack {
              List(viewModel.downloadedFiles, id: \.self) { Text($0) }
              Text("Storage Taken: \(viewModel.storageTaken)")
          }
          .onAppear(perform: viewModel.loadFiles)
      }
  }
  
  class WebViewCoordinator: NSObject, WKNavigationDelegate {
      weak var filesViewModel: FilesViewModel?
  
      init(filesViewModel: FilesViewModel? = nil) {
          self.filesViewModel = filesViewModel
      }
  }
  

4. Value of type WebViewCoordinator has no member getDocumentsDirectory #

• 问题：getDocumentsDirectory是全局函数，类中调用需确保作用域。
• 修复：将全局函数转为FileManager扩展，调用更规范：

  extension FileManager {
      static func getDocumentsDirectory() -> URL {
          let paths = self.default.urls(for: .documentDirectory, in: .userDomainMask)
          return paths[0]
      }
  }
  
  // Coordinator中调用方式
  let destinationURL = FileManager.getDocumentsDirectory().appendingPathComponent("\(sanitizeFileName(fileName: title)).mp4")
  

5. Value of type WebViewCoordinator has no member sanitizeFileName #

• 问题：同全局函数调用问题，直接调用全局函数即可，无需修改函数本身。

6. Value of type [URLResourceKey: Any] has no member totalFileAllocatedSize #

• 问题：原NSURL的fileSize()方法未完成，获取文件大小的方式错误。
• 修复：完善URL扩展的fileSize()方法：

  extension URL {
      func fileSize() -> Int {
          guard let attributes = try? FileManager.default.attributesOfItem(atPath: path) else { return 0 }
          return attributes[.size] as? Int ?? 0
      }
  }
  
  // 计算存储占用的调用方式
  let size = files.reduce(0, { $0 + $1.fileSize() })
  

完整修复后的代码 #

import SwiftUI
import WebKit

// 统一通知名称定义
extension Notification.Name {
    static let downloadCompleted = Notification.Name("DownloadCompleted")
}

@main
struct UDOWNLOADERZApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

struct ContentView: View {
    var body: some View {
        TabView {
            BrowserView()
                .tabItem { Label("Browser", systemImage: "globe") }
            FilesView()
                .tabItem { Label("Files", systemImage: "folder") }
            SettingsView()
                .tabItem { Label("Settings", systemImage: "gearshape") }
        }
    }
}

struct BrowserView: View {
    @State private var webView = WKWebView()
    @State private var coordinator: WebViewCoordinator?

    var body: some View {
        WebView(webView: $webView)
            .onAppear {
                if let url = URL(string: "https://youtube.com") {
                    webView.load(URLRequest(url: url))
                }
                coordinator = WebViewCoordinator()
                webView.navigationDelegate = coordinator
            }
    }
}

struct WebView: UIViewRepresentable {
    @Binding var webView: WKWebView

    func makeUIView(context: Context) -> WKWebView { webView }
    func updateUIView(_ uiView: WKWebView, context: Context) {}
}

class WebViewCoordinator: NSObject, WKNavigationDelegate {
    weak var filesViewModel: FilesViewModel?

    init(filesViewModel: FilesViewModel? = nil) {
        self.filesViewModel = filesViewModel
    }

    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        let jsCode = """
        (function() {
            var video = document.querySelector('video');
            var audio = document.querySelector('audio');
            var mediaElement = video || audio;
            if (mediaElement) {
                return {
                    src: mediaElement.src,
                    title: document.title || mediaElement.getAttribute('title') || 'Unknown'
                };
            }
            return null;
        })();
        """
        
        webView.evaluateJavaScript(jsCode) { [weak self] result, error in
            guard let resultDict = result as? [String: String],
                  let urlString = resultDict["src"],
                  let title = resultDict["title"],
                  let url = URL(string: urlString) else { return }
            
            self?.downloadContent(url: url, title: title)
        }
    }

    func downloadContent(url: URL, title: String) {
        DispatchQueue.global().async {
            let destinationURL = FileManager.getDocumentsDirectory().appendingPathComponent("\(sanitizeFileName(fileName: title)).mp4")

            URLSession.shared.downloadTask(with: url) { tempURL, _, error in
                guard let tempURL = tempURL, error == nil else { return }
                do {
                    try FileManager.default.moveItem(at: tempURL, to: destinationURL)
                    DispatchQueue.main.async {
                        NotificationCenter.default.post(name: .downloadCompleted, object: nil)
                        self.filesViewModel?.reloadFilesList()
                    }
                } catch {
                    print("Download failed: \(error.localizedDescription)")
                }
            }.resume()
        }
    }
}

class FilesViewModel: ObservableObject {
    @Published var downloadedFiles = [String]()
    @Published var storageTaken: String = ""

    func loadFiles() {
        DispatchQueue.global().async {
            do {
                let files = try FileManager.default.contentsOfDirectory(at: FileManager.getDocumentsDirectory(), includingPropertiesForKeys: nil, options: [])
                DispatchQueue.main.async {
                    self.downloadedFiles = files.map { $0.lastPathComponent }
                    self.calculateStorageTaken(files: files)
                }
            } catch {
                print("Failed to load files: \(error.localizedDescription)")
            }
        }
    }

    func reloadFilesList() { loadFiles() }

    private func calculateStorageTaken(files: [URL]) {
        let size = files.reduce(0, { $0 + $1.fileSize() })
        storageTaken = ByteCountFormatter.string(fromByteCount: Int64(size), countStyle: .file)
    }
}

struct FilesView: View {
    @StateObject private var viewModel = FilesViewModel()

    var body: some View {
        VStack {
            List(viewModel.downloadedFiles, id: \.self) { Text($0) }
            Text("Storage Taken: \(viewModel.storageTaken)")
        }
        .onAppear(perform: viewModel.loadFiles)
        .onReceive(NotificationCenter.default.publisher(for: .downloadCompleted)) { _ in
            viewModel.reloadFilesList()
        }
    }
}

struct SettingsView: View {
    var body: some View {
        VStack {
            Text("Contact: Udownloaderz2@proton.me")
            Text("Twitter: N/A")
        }
    }
}

extension FileManager {
    static func getDocumentsDirectory() -> URL {
        let paths = self.default.urls(for: .documentDirectory, in: .userDomainMask)
        return paths[0]
    }
}

func sanitizeFileName(fileName: String) -> String {
    let invalidCharacters = CharacterSet(charactersIn: "\\/:*?\"<>|")
    return fileName.components(separatedBy: invalidCharacters).joined(separator: "_")
}

extension URL {
    func fileSize() -> Int {
        guard let attributes = try? FileManager.default.attributesOfItem(atPath: path) else { return 0 }
        return attributes[.size] as? Int ?? 0
    }
}

内容的提问来源于stack exchange，提问作者rights4a