Documentsフォルダ内のファイル一覧出力
private func getFileNames(dir:String) -> [String]{
    let path = NSHomeDirectory().stringByAppendingPathComponent("Documents/" + dir)
    var error: NSError? = nil
    let fileNames:[AnyObject] = NSFileManager.defaultManager().contentsOfDirectoryAtPath(path,error:&error)!
    var tmp:[String] = []
    for fileName:AnyObject in fileNames {
        tmp.append(fileName as String)
    }
    return tmp
}
private func logFileNames(){
    println("----------------- " + __FUNCTION__ + "---------------------")
    let files:[String] = self.getFileNames("")
    for n:String in files {
        println("\(n)")
    }
}