NSFileHandle fileHandleForWritingAtPath：返回null！

我的iPad应用程序有一个小的下载工具，我想用NSFileHandle附加数据。 问题是创build调用只返回空文件句柄。 可能是什么问题呢？ 这是应该创build我的文件句柄的三行代码：

NSString *applicationDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; self.finalPath = [applicationDocumentsDirectory stringByAppendingPathComponent: self.fileName]; NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath]; 

我检查了文件path，我没有看到任何错误。

TYIA

Answer 1

fileHandleForWritingAtPath不是“创build”调用。 该文档明确指出：“返回值：初始化的文件句柄，或者如果path中没有文件存在，则为零 ”（强调添加）。 如果你想创build文件，如果它不存在，你必须使用这样的东西：

  NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath]; if(output == nil) { [[NSFileManager defaultManager] createFileAtPath:self.finalPath contents:nil attributes:nil]; output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath]; } 

如果你想附加到文件，如果它已经存在，使用类似[output seekToEndOfFile] 。 您的完整代码将如下所示：

  NSString *applicationDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject]; self.finalPath = [applicationDocumentsDirectory stringByAppendingPathComponent: self.fileName]; NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath]; if(output == nil) { [[NSFileManager defaultManager] createFileAtPath:self.finalPath contents:nil attributes:nil]; output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath]; } else { [output seekToEndOfFile]; } 

Answer 2

获取文档目录path

 +(NSURL *)getDocumentsDirectoryPath { return [[[NSFileManager defaultManager]URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask]lastObject]; } 

将文本保存到文件结尾

如果文件不存在，创build它并写入数据

 +(void)saveText:(NSString *)textTobeSaved atPath:(NSString*)fileName { NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName]; NSString *path = [[self getDocumentsDirectoryPath].path stringByAppendingPathComponent:filePath]; NSFileHandle *fileHandler = [NSFileHandle fileHandleForWritingAtPath:path]; if(fileHandler == nil) { [[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil]; fileHandler = [NSFileHandle fileHandleForWritingAtPath:path]; } else { textTobeSaved = [NSString stringWithFormat:@"\n-----------------------\n %@",textTobeSaved]; [fileHandler seekToEndOfFile]; } [fileHandler writeData:[textTobeSaved dataUsingEncoding:NSUTF8StringEncoding]]; [fileHandler closeFile]; } 

从指定文件名的文件中获取文本

 +(NSString *)getTextFromFilePath:(NSString *)fileName { NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName]; NSString *path = [[self getDocumentsDirectoryPath].path stringByAppendingPathComponent:filePath]; NSLog(@"%@",path); if(path!=nil) { NSString *savedString = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil]; return savedString; }else{ return @""; } } 

删除文件

 +(void)deleteFile:(NSString *)fileName { NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName]; NSString *path = [[self getDocumentsDirectoryPath].path stringByAppendingPathComponent:filePath]; NSFileHandle *fileHandler = [NSFileHandle fileHandleForWritingAtPath:path]; if(fileHandler != nil) { [[NSFileManager defaultManager]removeItemAtPath:path error:nil]; } }