Swift："Type of expression is ambiguous without more context" 与 URLSession

Question

我正在尝试执行以下代码以在 WKWebView 中捕获 PDF 下载：

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    if let url = navigationAction.request.url {

        print("fileDownload: check ::  \(url)")

        let extention = "\(url)".suffix(4)

        if extention == ".pdf" {
            print("fileDownload: redirect to download events. \(extention)")
            DispatchQueue.main.async {
                self.downloadPDF(tempUrl: "\(url)")
            }
            decisionHandler(.cancel)
            return
        }

    }

    decisionHandler(.allow)
}

func downloadPDF(tempUrl:String){
    print("fileDownload: downloadPDF")
    guard let url = URL(string: tempUrl) else { return }
    let urlSession = URLSession(configuration: .default, delegate: self, delegateQueue: OperationQueue())
    let downloadTask = urlSession.downloadTask(with: url)
    downloadTask.resume()
    //showHUD(isShowBackground: true); //show progress if you need
}
func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
    print("fileDownload: documentInteractionControllerViewControllerForPreview")
    return self
}
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    // create destination URL with the original pdf name
    print("fileDownload: urlSession")
    guard let url = downloadTask.originalRequest?.url else { return }
    print("fileDownload: urlSession \(url)")
    let documentsPath = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
    let destinationURL = documentsPath.appendingPathComponent(url.lastPathComponent)
    // delete original copy
    try? FileManager.default.removeItem(at: destinationURL)
    // copy from temp to Document
    do {
        try FileManager.default.copyItem(at: location, to: destinationURL)
        myViewDocumentsmethod(PdfUrl:destinationURL)
        print("fileDownload: downloadLocation", destinationURL)
        DispatchQueue.main.async {
            NBMaterialToast.showWithText(self.view, text: "Download Completed", duration: NBLunchDuration.long)
        }
    } catch let error {
        print("fileDownload: error \(error.localizedDescription)")
    }
   // dismissHUD(isAnimated: false); //dismiss progress
}
func myViewDocumentsmethod(PdfUrl:URL){
    print("fileDownload: myViewDocumentsmethod \(PdfUrl)")
    DispatchQueue.main.async {
        let controladorDoc = UIDocumentInteractionController(url: PdfUrl)
        controladorDoc.delegate = self
        controladorDoc.presentPreview(animated: true)
    }
}

如本帖所建议：

但是 Xcode 给我以下错误：

“表达式类型不明确，没有更多上下文”

对于 downloadPDF 函数中的以下行：

let urlSession = URLSession(configuration: .default, delegate: self, delegateQueue: OperationQueue())

如您在随附的屏幕截图中所见。

有什么解决办法吗？

Answer 1

将 URLSessionDelegate 协议继承给您的 class。

Swift："Type of expression is ambiguous without more context" 与 URLSession

Swift: "Type of expression is ambiguous without more context" with URLSession

xcode

ios

swift

wkwebview