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How do you save/export a CSV files to an extrenal flash drive?

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How do you save/export a CSV files to an extrenal flash drive? I know you're susposed to use UIDocumentPickerViewController, but I am confused how to do that with the code I have below. An pointer or direction would be appreciated!

Thank you,


import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        // Do any additional setup after loading the view.

    @IBAction func generateCSVFile(_ sender: Any) {

        let sFileName = "test.csv"

        let documentDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String

        let documentURL = URL(fileURLWithPath: documentDirectoryPath).appendingPathComponent(sFileName)

        let output = OutputStream.toMemory()

        let csvWriter = CHCSVWriter(outputStream: output, encoding: String.Encoding.utf8.rawValue, delimiter: ",".utf16.first!)

        // HEADER


        var arrOfEmployeeData = [[String]]()

        arrOfEmployeeData.append(["1", "Company 1"])
        arrOfEmployeeData.append(["2", "Company 2"])
        arrOfEmployeeData.append(["3", "Company 3"])

        for(elements) in arrOfEmployeeData.enumerated()
            csvWriter?.writeField(elements.element[0]) // ID
            csvWriter?.writeField(elements.element[1]) // Name
            csvWriter?.writeField(elements.element[2]) // Age
            csvWriter?.writeField(elements.element[3]) // Designation




        let buffer = (output.property(forKey: .dataWrittenToMemoryStreamKey) as? Data)!

            try buffer.write(to: documentURL)



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