I have REAL misunderstanding with MFMailComposeVie

Question

I create a csv file and try to send it by e-mail. Displays a window to send mail, but is not filled with body of the email, and no attached file. Application hangs with this screen:

button "Cancel" does not work. After a few seconds in the console appears:

viewServiceDidTerminateWithError: Error Domain=_UIViewServiceInterfaceErrorDomain Code=3 "The operation couldn’t be completed. (_UIViewServiceInterfaceErrorDomain error 3.)" UserInfo=0x7f8409f29b50 {Message=Service Connection Interrupted}

<MFMailComposeRemoteViewController: 0x7f8409c89470> timed out waiting for fence barrier from com.apple.MailCompositionService

There is my code:

func actionSheet(actionSheet: UIActionSheet!, clickedButtonAtIndex buttonIndex: Int) {
    if buttonIndex == 0 {
        println("Export!")

        var csvString = NSMutableString()
        csvString.appendString("Date;Time;Systolic;Diastolic;Pulse")

        for tempValue in results {     //result define outside this function

            var tempDateTime = NSDate()
            tempDateTime = tempValue.datePress
            var dateFormatter = NSDateFormatter()
            dateFormatter.dateFormat = "dd-MM-yyyy"
            var tempDate = dateFormatter.stringFromDate(tempDateTime)
            dateFormatter.dateFormat = "HH:mm:ss"
            var tempTime = dateFormatter.stringFromDate(tempDateTime)

            csvString.appendString("\n\(tempDate);\(tempTime);\(tempValue.sisPress);\(tempValue.diaPress);\(tempValue.hbPress)")
        }

        let fileManager = (NSFileManager.defaultManager())
        let directorys : [String]? = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory,NSSearchPathDomainMask.AllDomainsMask, true) as? [String]

        if ((directorys) != nil) {

            let directories:[String] = directorys!;
            let dictionary = directories[0];
            let plistfile = "bpmonitor.csv"
            let plistpath = dictionary.stringByAppendingPathComponent(plistfile);

            println("\(plistpath)")

            csvString.writeToFile(plistpath, atomically: true, encoding: NSUTF8StringEncoding, error: nil)

            var testData: NSData = NSData(contentsOfFile: plistpath)

            var myMail: MFMailComposeViewController = MFMailComposeViewController()

            if(MFMailComposeViewController.canSendMail()){

                myMail = MFMailComposeViewController()
                myMail.mailComposeDelegate = self

                // set the subject
                myMail.setSubject("My report")

                //Add some text to the message body
                var sentfrom = "Mail sent from BPMonitor"
                myMail.setMessageBody(sentfrom, isHTML: true)

                myMail.addAttachmentData(testData, mimeType: "text/csv", fileName: "bpmonitor.csv")

                //Display the view controller
                self.presentViewController(myMail, animated: true, completion: nil)
            }
            else {
                var alert = UIAlertController(title: "Alert", message: "Your device cannot send emails", preferredStyle: UIAlertControllerStyle.Alert)
                alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.Default, handler: nil))
                self.presentViewController(alert, animated: true, completion: nil)


            }
        }
        else {
            println("File system error!")
        }
    }
}

Trying instead to send mail using UIActivityViewController:

let fileURL: NSURL = NSURL(fileURLWithPath: plistpath)
let actViewController = UIActivityViewController(activityItems: [fileURL], applicationActivities: nil)
self.presentViewController(actViewController, animated: true, completion: nil)

See approximately the same screen to send e-mail, which after a while returning to the previous screen. In the console, now another error:

viewServiceDidTerminateWithError: Error Domain=_UIViewServiceInterfaceErrorDomain Code=3 "The operation couldn’t be completed. (_UIViewServiceInterfaceErrorDomain error 3.)" UserInfo=0x7faab3296ad0 {Message=Service Connection Interrupted}
Errors encountered while discovering extensions: Error Domain=PlugInKit Code=13 "query cancelled" UserInfo=0x7faab3005890 {NSLocalizedDescription=query cancelled}
<MFMailComposeRemoteViewController: 0x7faab3147dc0> timed out waiting for fence barrier from com.apple.MailCompositionService

There was something about PlugInKit.

Trying instead UIActivityViewController using UIDocumentInteractionController:

let docController = UIDocumentInteractionController(URL: fileURL)
docController.delegate = self
docController.presentPreviewAnimated(true)
...

func documentInteractionControllerViewControllerForPreview(controller: UIDocumentInteractionController!) -> UIViewController! {
    return self
}

I see this screen with contents a CSV-file: http://prntscr.com/4ilgax I press button export in top-right and see this screen http://prntscr.com/4ilguk where I choose MAIL and and for several seconds I see http://prntscr.com/4ilh2h Then returns to displaying the contents of the file! In the console the same messages as when using UIActivityViewController.

Answer 1

It has nothing to do with Swift. It's an issue with the mail composer that's been around forever it seems. That thing is extremely picky, from failing with timeouts to sending delegate messages even when cancelled.

The workaround everyone uses is to create a global mail composer (for example in a singleton), and every single time reinitializing it when you need it. This ensures the mail composer is always around when the OS needs it, but also that it is free of any crap when you want to reuse it.

So create a strong (as global as possible) variable holding the mail composer and reset it every time you want to use it.