如何在SwiftUI中位于Apple的Files应用程序的文件夹中写入文件？

正如我已经在评论中发布的那样，您不能以编程方式将文件保存到APP捆绑包之外。您可以使用UIDocumentInteractionController并要求用户选择应该将文件写入的位置。

所以，如果你与SwiftUI这个工作变得比普通故事板的方法有点复杂，你可以在此看到帖子，因为你需要实现UIViewControllerRepresentable的UIDocumentInteractionController：

struct DocumentInteractionController: UIViewControllerRepresentable {

    fileprivate var isExportingDocument: Binding<Bool>
    fileprivate let viewController = UIViewController()
    fileprivate let documentInteractionController: UIDocumentInteractionController

    init(_ isExportingDocument: Binding<Bool>, url: URL) {
        self.isExportingDocument = isExportingDocument
        documentInteractionController = .init(url: url)
    }

    func makeUIViewController(context: UIViewControllerRepresentableContext<DocumentInteractionController>) -> UIViewController { viewController }

    func updateUIViewController(_ controller: UIViewController, context: UIViewControllerRepresentableContext<DocumentInteractionController>) {
        if isExportingDocument.wrappedValue && documentInteractionController.delegate == nil {
            documentInteractionController.uti = documentInteractionController.url?.typeIdentifier ?? "public.data, public.content"
            documentInteractionController.name = documentInteractionController.url?.localizedName
            documentInteractionController.presentOptionsMenu(from: controller.view.frame, in: controller.view, animated: true)
            documentInteractionController.delegate = context.coordinator
            documentInteractionController.presentPreview(animated: true)
        }
    }

    func makeCoordinator() -> Coordintor { .init(self) }
}

及其协调人：

class Coordintor: NSObject, UIDocumentInteractionControllerDelegate {
    let documentInteractionController: DocumentInteractionController
    init(_ controller: DocumentInteractionController) {
        documentInteractionController = controller
    }
    func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController { documentInteractionController.viewController }

    func documentInteractionControllerDidDismissOptionsMenu(_ controller: UIDocumentInteractionController) {
        controller.delegate = nil
        documentInteractionController.isExportingDocument.wrappedValue = false
    }
}

现在，您可以创建DocumentInteraction视图及其预览：

struct DocumentInteraction: View {
    @State private var isExportingDocument = false
    var body: some View {
        VStack {
            Button("Export Document") { self.isExportingDocument = true }
            .background(DocumentInteractionController($isExportingDocument,
                url: Bundle.main.url(forResource: "sample", withExtension: "pdf")!))
        }
    }
}

struct DocumentInteraction_Previews: PreviewProvider {
    static var previews: some View { DocumentInteraction() }
}

您还将需要那些帮助者：

extension URL {
    var typeIdentifier: String? { (try? resourceValues(forKeys: [.typeIdentifierKey]))?.typeIdentifier }
    var localizedName: String? { (try? resourceValues(forKeys: [.localizedNameKey]))?.localizedName }
}

样例项目