Question

就像SO上的答案一样，我试图附加一个文本文件。我的代码是这样的：

if countdownTimer > 0 {
   let dir = NSFileManager.defaultManager().URLsForDirectory(NSSearchPathDirectory.CachesDirectory, inDomains: NSSearchPathDomainMask.UserDomainMask).first!
   let fileurl = dir.URLByAppendingPathComponent(fileName)

   let date = NSDate()
   let calendar = NSCalendar.currentCalendar()
   let hour = calendar.component(.Hour, fromDate: date)
   let minutes = calendar.component(.Minute, fromDate: date)
   let seconds = calendar.component(.Second, fromDate: date)

   newLine = "\(hour):\(minutes):\(seconds),\(someValue),\(someValue)\n"

   let data = newLine.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!


   if NSFileManager.defaultManager().fileExistsAtPath(fileurl!.path!) {
      do {
          let fileHandle = try NSFileHandle(forWritingToURL: fileurl!)

          fileHandle.seekToEndOfFile()
          fileHandle.writeData(data)
          fileHandle.closeFile()
       } catch {
          print("Can't open fileHandle \(error)")
       }
   } else {

    }
        countdownTimer -= 1
}

我的实现的不同之处在于我在单独的事件上创建文件（并且我确定文件在附加之前存在）并且附加文本文件在每秒循环的计时器内。我究竟做错了什么？感谢。

Answer 1

我编写的代码可以帮助您了解可能出错的地方。

首先创建Error类型和文件名，我们将记录我们的信息。

let file = "logger1.txt"

enum Throwing: Error {
    case impossibleToWrite
    case impossibleToRead
}

比writeToFile和readFromFile两个函数。

func writeToFile(file:String, log: String) throws {

    if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {

        let path = dir.appendingPathComponent(file)

        do {
            let writer = try FileHandle(forWritingTo: path)
            writer.seekToEndOfFile()
            writer.write(log.data(using: String.Encoding.utf8)!)
            writer.closeFile()
        }
        catch {
            throw Throwing.impossibleToWrite
        }
    }
}

func readFromFile(file:String) throws {

    if let dir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first {

        let path = dir.appendingPathComponent(file)

        do {
            let text = try String(contentsOf: path, encoding: String.Encoding.utf8)
            print(text)
        }
        catch {
            throw Throwing.impossibleToRead
        }
    }
}

比将循环并使用日期创建日志的小循环。用法试试！是不好的做法，但为了测试目的，这是可以的。

func logTimeInLoop() {

    for _ in 0..<10 {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd HH:mm:ss.SSS "
        let text = formatter.string(from: Date()) + "\n"

        try! writeToFile(file: file, log: text)
    }

    try! readFromFile(file: file)
}

这是文件中数据的输出。

附加文本文件不起作用

1 个答案: