Download files from Dropbox (swift & SDK 1.3.13)

Hello,

I noticed that DBRestClient is asynchronous, it means that When I download file from Dropbox, I cannot read it immediately.
I put in place a While (to wait upload completed) but I have not success, could you please help?

Thanks
Sébastien

My VIEW code:

class ViewController: UIViewController, DBRestClientDelegate {
    private var FileLoaded = false

    ...

    @IBAction func btDownload(sender: AnyObject) {
        txtFileReader.text=""
        txtLogs.insertText("Start DL file \n")
        let tmpDirectory = NSTemporaryDirectory()
        let myFilename = tmpDirectory.stringByAppendingPathComponent("Test.txt")
        FileLoaded=false
        dbRestClient?.loadFile("/MyFolder/Test.txt", intoPath: myFilename)
        while FileLoaded {
            txtFileReader.text = String(contentsOfFile: myFilename, encoding: NSUTF8StringEncoding, error: nil)
        }
        txtLogs.insertText(" \(myFilename) \n")
        txtLogs.insertText("End DL file \n")
    }

    func restClient(client: DBRestClient!, loadedFile localPath: String, contentType contentType: String, metadata metadata: DBMetadata!){
        println("File loaded into path: \(localPath)")
        FileLoaded=true
    }
    func restClient(client: DBRestClient!, loadFileFailedWithError error: NSError!){
        println("LoadFile failed with error: \(error)")
    }