Save WS Call to file [Swift 2.3]

FileSave.swift

    private func saveToFile(string : String, url : String, method : String) {
        guard let dir = NSFileManager.defaultManager().URLsForDirectory(NSSearchPathDirectory.DocumentDirectory, inDomains: NSSearchPathDomainMask.UserDomainMask).last else { return }
        guard let fileurl =  dir.URLByAppendingPathComponent("log.txt") else { return }
        
        let dateFormatter = NSDateFormatter()
        dateFormatter.dateFormat = "yyyy-MM-dd' 'HH:mm:ssZZZZZ"
        let string = dateFormatter.stringFromDate(NSDate()) + " [" + method + "] " + url + "\n" + string + "\n"
        let data = string.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!
        
        if NSFileManager.defaultManager().fileExistsAtPath(fileurl.path!) {
            if let fileHandle = try? NSFileHandle(forWritingToURL : fileurl) {
                fileHandle.seekToEndOfFile()
                fileHandle.writeData(data)
                fileHandle.closeFile()
            }
            else {
                print("Can't open fileHandle ")
            }
        }
        else {
            do {
                try data.writeToURL(fileurl, options: .DataWritingAtomic)
            }catch {
                print("Can't write \(error)")
            }
        }
    }