將writeToFile：原子地覆蓋數據？

Question

真的很簡單的問題，但它似乎沒有在蘋果的文檔中很清楚。

請問writeToFile:atomically:是否爲NSData, NSArray等覆蓋文件上的現有數據？

Answer 1

是的。它會。

以下是一些要傳遞30個字符限制的字符。

Answer 2

方法writeToFile:atomically:總是覆蓋文件，不管atomically:是或否。

從Apple docs（NSData的，部分 「保存數據」）的信息：

The NSData class and its subclasses provide methods to quickly and easily save their contents to disk. To minimize the risk of data loss, these methods provide the option of saving the data atomically. Atomic writes guarantee that the data is either saved in its entirety, or it fails completely. The atomic write begins by writing the data to a temporary file. If this write succeeds, then the method moves the temporary file to its final location.

沒有一個字有關，如果文件存在檢查。

例如，對於方法copyItemAtPath:toPath:error:在docs（的NSFileManager，部分討論）專門寫了這樣的檢查：

If a file with the same name already exists at dstPath, this method stops the copy attempt and returns an appropriate error.