func createSomeFile() {

    var output = (some NSData to output to file)


    let fileName = NSTemporaryDirectory().stringByAppendingPathComponent("filename.ext")
    let url: NSURL! = NSURL(fileURLWithPath: fileName)

    var dataToWrite = output.dataUsingEncoding(NSUTF8StringEncoding)
    dataToWrite?.writeToFile(url.absoluteString!, atomically: true)

    documentController = UIDocumentInteractionController(URL: url)
    documentController.UTI = "com.someUTI"
    documentController.delegate = self

    documentController.presentOpenInMenuFromRect(CGRectZero, inView: self, animated: true)
}

documentController.presentOpenInMenuFromRect(CGRectZero, inView: self.view, animated: true)