Add Share Button to iOS 9 App

@IBAction func export(sender: UIBarButtonItem) {        
    if let data = prepareCSVData() {
        let filename = getDocumentsDirectory().stringByAppendingPathComponent("data.csv")
        
        data.writeToFile(filename, atomically: true)
        
        let url = NSURL(fileURLWithPath: filename)
        
        let activityViewController = UIActivityViewController(activityItems: [url], applicationActivities: nil)
        
        if let popoverController = activityViewController.popoverPresentationController {
            popoverController.barButtonItem = sender
        }

        presentViewController(activityViewController, animated: true, completion: nil)

    } else {
        NSLog("Unable to prepare data")
    }
}

The important line is where you set up the popoverController. Without that, it will crash on iPad.

Send Mail with Attachment in iOS

if MFMailComposeViewController.canSendMail() {
    let data = prepareCSVData()
    
    let mailController = MFMailComposeViewController()
    mailController.mailComposeDelegate = self
    mailController.setSubject("Data Export")
    mailController.setMessageBody("Attached is a CSV file containing your data.", isHTML: false)
    
    // Add attachment
    if let data = data {
        mailController.addAttachmentData(data, mimeType: "text/comma-separated-values", fileName: "headaches.csv")
        
        presentViewController(mailController, animated: true, completion: nil)
    } else {
        NSLog("No data")
    }
}