class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        let str = "Test Message"
        let url = self.getDocumentsDirectory().appendingPathComponent("message.txt")

        do {
            try str.write(to: url, atomically: true, encoding: .utf8)
        } catch {
            print(error.localizedDescription)
        }

    }

    func getDocumentsDirectory() -> URL {
        // find all possible documents directories for this user
        let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)

        // just send back the first one, which ought to be the only one
        return paths[0]
    }

}