Ios swift – Upload PDF from shared local storage in iOS (Drive, OneDrive, Dropbox..) to server with Ktor Fails

I managed to find the reason behind this issue and a solution.

The problem: in iOS cloud storage (Google Drive, OneDrive, Dropbox,..) provide placeholders not the real URI to the file and unless the file is downloaded locally you cannot get the Data of the file. Even it seems to you that you can access files from Google Drive, or any other cloud storage from the shared storage in iOS u can not get the data only if they are downloaded in the device.

The solution: There are 2 solution for this problem:

1. Use each Cloud service/API separately to manage access remote files. that way you need to implement each API separately.

2. Display a preview of the file using documentInteractionController and it will take care of loading the file, and then you got access to data.

I personally found the second solution more efficient, because in my case i just need the data of the selected file and displaying the file to the user is not problem for me so i am not limited to implement the logic only in the background.

here is my solution:

lateinit var documentInteractionDelegate: DocumentInteractionControllerDelegate
val documentInteractionController = UIDocumentInteractionController()

val documentPickerController = UIDocumentPickerViewController(
    forOpeningContentTypes = listOf(UTTypePDF)
)

documentPickerController.allowsMultipleSelection = false

val documentPickerDelegate = remember {
    object : NSObject(), UIDocumentPickerDelegateProtocol {
        override fun documentPicker(
            controller: UIDocumentPickerViewController,
            didPickDocumentAtURL: NSURL
        ) {
            val accessing = didPickDocumentAtURL.startAccessingSecurityScopedResource()
            if (accessing) {
                    documentInteractionController.URL = didPickDocumentAtURL
                    documentInteractionDelegate =
                        DocumentInteractionControllerDelegate(
                            fileUrl = documentInteractionController.URL,
                            handelDocInfoCallback = handelDocInfo
                        )
                    documentInteractionController.delegate = documentInteractionDelegate
                    presentDocumentInteractionController(documentInteractionController)

                didPickDocumentAtURL.stopAccessingSecurityScopedResource()
            }
            controller.dismissViewControllerAnimated(true, null)
        }

        override fun documentPickerWasCancelled(controller: UIDocumentPickerViewController) {
            println("$TAG Document picker was cancelled.")
        }
    }
}

and this the DocumentInteractionControllerDelegate class:

@OptIn(ExperimentalForeignApi::class)
class DocumentInteractionControllerDelegate(
    private val fileUrl: NSURL?,
    val handelDocInfoCallback: (DocumentInfo) -> Unit
) : NSObject(),
    UIDocumentInteractionControllerDelegateProtocol {

    /**
     * Specifies the UIViewController that will host the preview.
     */
    override fun documentInteractionControllerViewControllerForPreview(controller: UIDocumentInteractionController): UIViewController {
        println("Providing the view controller for document preview.")
        return UIApplication.sharedApplication.keyWindow?.rootViewController ?: UIViewController()
    }

    /**
     * Optional: Called when the preview is about to begin
     * Called before the document preview begins.
     */
    override fun documentInteractionControllerWillBeginPreview(controller: UIDocumentInteractionController) {
        println("Document preview will begin.")
    }

    /**
     * Called when the document preview is done (e.g., dismissed)
     */
    @OptIn(BetaInteropApi::class)
    override fun documentInteractionControllerDidEndPreview(controller: UIDocumentInteractionController) {
        println("Document preview ended. ${fileUrl?.path}")
        // You can perform any action here after the preview has ended, like notifying the user or handling another task
        val accessible = fileUrl?.startAccessingSecurityScopedResource()
        println("Document preview ended. - accessible $accessible")
        if (accessible == true) {
            memScoped {
                val errorPtr: ObjCObjectVar<NSError?> = alloc<ObjCObjectVar<NSError?>>()
                val newData = fileUrl?.path?.let {
                    NSData.dataWithContentsOfFile(
                        it,
                        NSDataReadingUncached,
                        errorPtr.ptr
                    )
                }
                println("$TAG errorPtr: ${errorPtr.value}")
                println("$TAG newData: ${newData?.toByteArray()?.size}")
           
            }
            fileUrl?.stopAccessingSecurityScopedResource()
        }

    }

    /**
     * Returns the UIView that acts as the anchor for the preview animation.
     */
    override fun documentInteractionControllerViewForPreview(controller: UIDocumentInteractionController): UIView? {
        println("Providing view for document preview.")
        return UIApplication.sharedApplication.keyWindow?.rootViewController?.view
    }
}

fun presentDocumentInteractionController(documentInteractionController: UIDocumentInteractionController): Boolean {
    // Present the document interaction controller
    val displayed = try {
        documentInteractionController.presentPreviewAnimated(true)
    } catch (e: Exception) {
        e.printStackTrace()
        false
    }
    return displayed
}