Error UIAlert when trying to do unwindsegue

Question

I have a UIView which allow user to save some data with their desirable name before it can be view in the tableView

func saveFilesName() {
    let alert = UIAlertController(title: "Save As", message: "Please enter the file name", preferredStyle: .alert)
    alert.addTextField(configurationHandler: {(nameField) -> Void in
        nameField.placeholder = "Enter the file name"
        nameField.textAlignment = .center
    })
    alert.addTextField(configurationHandler: {(descField) -> Void in
        descField.placeholder = "Enter the your description"
        descField.textAlignment = .center
    })
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: { (actions: UIAlertAction) -> Void in
    }))

    alert.addAction(UIAlertAction(title: "Save", style: .default, handler: { (actions: UIAlertAction) -> Void in
        let nameFieldData = alert.textFields![0]
        let descFieldData = alert.textFields![1]
        self.fileName = nameFieldData.text!
        self.descData = descFieldData.text!
        print(alert.textFields![0])
        let saveCSV = self.saveCSVFiles()
        print(saveCSV.lastPathComponent)
    }))

    self.present(alert, animated: true, completion: nil)
}

the problems is when I ran the code above, it will come with this error: "while an existing transition or presentation is occurring; the navigation stack will not be updated." right before the alert will normally pop up then it crash and the alert doesn't work.

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    super.prepare(for: segue, sender: sender)

    guard let button = sender as? UIBarButtonItem, button === saveButton else {
        os_log("The save button was not pressed, cancelling", log: OSLog.default, type: .debug)
        return
    }

    saveFilesName()

    if fileName != nil {
    let nsurl = String(describing: csvFile)

    let name = fileName
    let description = descData
    let photo = UIImage(contentsOfFile: "defaultImage")
    let url = NSURL(fileURLWithPath: nsurl)

    csv = CSVData(name: name!, description: description!, photo: photo, url: url)
    }

}

since the alert is needed before I can append any data to the class model. Any help would be appreciated

so the flow you want is VC1 -> ShowAlert -> click SaveAction -> dismiss alert and show nextVC? — mfaani, Oct 27 '17 at 14:07
if that is what you want then you should place the `performsegue` call **inside** the `handler` of saveAction, so when save is clicked, the alert would be automatically dismissed and then it would show your nextVC — mfaani, Oct 27 '17 at 15:13
@Honey yes, that exactly what I wanted. so, you mean I need IBAction instead of an outlet ? and put performsegue in there right ? — JameS, Oct 27 '17 at 16:10

score 1 · Accepted Answer · answered Oct 27 '17 at 16:28

You don't need another IBAction, you can benefit from the user tapping on the Save button. Right?

inside your Save's handler ie here:

alert.addAction(UIAlertAction(title: "Save", style: .default, handler: { (actions: UIAlertAction) -> Void in
        let nameFieldData = alert.textFields![0]
        let descFieldData = alert.textFields![1]
        self.fileName = nameFieldData.text!
        self.descData = descFieldData.text!
        print(alert.textFields![0])
        let saveCSV = self.saveCSVFiles()
        print(saveCSV.lastPathComponent)
    }))

add the performSegue(withIdentifier: "YOUR_SEGUE_IDENTIFIER", sender: self) right after print(saveCSV.lastPathComponent)

so once you click save, it will dismiss the alert and then perform that segue.

This would trigger your prepare(for segue...)

Error UIAlert when trying to do unwindsegue

1 Answers1