How can I write a file in a folder located at Apple's Files App in SwiftUI?

Question

I followed the Swift project UsingFiles github and its video to write files in my SwiftUI project. The project UsingFiles can write files to Files APP and then the writing files

Answer 1

As I have already posted in comments you can NOT programmatically save a file out of your APP Bundle. You can use a UIDocumentInteractionController and ask the user to choose the location where the file is supposed to be written.

So if you are working with SwiftUI this gets a bit more complicated than the regular Storyboard approach as you can see in this post because you need to implement UIViewControllerRepresentable for UIDocumentInteractionController:

---

struct DocumentInteractionController: UIViewControllerRepresentable {

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

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

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

    func updateUIViewController(_ controller: UIViewController, context: UIViewControllerRepresentableContext) {
        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) }
}

---

And its Coordinator:

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
    }
}

---

Now you can create your DocumentInteraction View and its previews:

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() }
}

---

You will need those helpers as well:

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

---

Sample project