Open File Dialog crashes in Swift

Question

I would like to use the open file dialogs from NSFilemanager but my code crashes sometimes and sometimes works and I do not know why. Sometimes it works 100%, sometimes the

Answer 1

The restrictions of the User Interface (UI) Calls, which are not Thread-Save, can be solved, when you use the following code, which executes a block of commands in the main thread asynchronously:

dispatch_async(dispatch_get_main_queue())
{
    // This commands are executed ansychronously
}

So you have to write your own functions for every built-in-function, which is not thread-save like this (example with the open file dialog):

func not (b: Bool) -> Bool
{
    return (!b)
}

func suspendprocess (t: Double)
{
    var secs: Int = Int(abs(t))
    var nanosecs: Int = Int(frac(abs(t)) * 1000000000)
    var time = timespec(tv_sec: secs, tv_nsec: nanosecs)
    let result = nanosleep(&time, nil)
}

func openfiledialog (windowTitle: String, message: String, filetypelist: String) -> String
{
    var path: String = ""
    var finished: Bool = false

    suspendprocess (0.02) // Wait 20 ms., enough time to do screen updates regarding to the background job, which calls this function
    dispatch_async(dispatch_get_main_queue())
    {
        var myFiledialog: NSOpenPanel = NSOpenPanel()
        var fileTypeArray: [String] = filetypelist.componentsSeparatedByString(",")

        myFiledialog.prompt = "Open"
        myFiledialog.worksWhenModal = true
        myFiledialog.allowsMultipleSelection = false
        myFiledialog.canChooseDirectories = false
        myFiledialog.resolvesAliases = true
        myFiledialog.title = windowTitle
        myFiledialog.message = message
        myFiledialog.allowedFileTypes = fileTypeArray

        let void = myFiledialog.runModal()

        var chosenfile = myFiledialog.URL // Pathname of the file

        if (chosenfile != nil)
        {
            path = chosenfile!.absoluteString!
        }
        finished = true
    }

    while not(finished)
    {
        suspendprocess (0.001) // Wait 1 ms., loop until main thread finished
    }

    return (path)
}

Please note, that the block is called asynchronously, that means you have to check, if the block has been processed and is finished or not. So I add a boolean variable "finsihed" which shows, when the block reaches its end. Without this you do not get the pathname but only an empty string.

If you are interested, I will post my savefiledialog-function, too. Please leave a comment if so.

Answer 2

Most of the User Interface (UI) Calls are not Thread-Save, that means that they only work without crash and unusual behaviour in the main-thread.

This is the problem with NSOpenPanel Calls, too. When calling from the main-thread everything is OK.