使用NSFileHandle进行文件读/写的示例 [英] Example for file read/write with NSFileHandle

问题描述

有没有很好的例子做文件读/写块的目标C？我是新的Objective-C和iPhone API，这里是我写的示例代码。有没有更好的方法来做到这一点？

   - （void）performFileOperation 
 {
 @try {
 
 NSFileHandle * inputFileHandle; 
 NSFileHandle * outputFileHandle; 
 
 //检查输出文件是否存在，如果没有创建新文件。 
 NSFileManager * morphedFileManager; 
 
 outputFileManager = [NSFileManager defaultManager]; 
 
 if（[outputFileManager fileExistsAtPath：self.outputFilePath] == NO）
 {
 NSLog（@Output file does not exist，creating a new one）; 
 [outputFileManager createFileAtPath：self.outputFilePath 
 contents：nil 
 attributes：nil]; 
} 
 
 NSData * inputDataBuffer; 
 
 inputFileHandle = [NSFileHandle fileHandleForReadingAtPath：self.inputFilePath]; 
 
 NSAssert（inputFileHandle！= nil，@无法打开输入文件的句柄）; 
 
 outputFileHandle = [NSFileHandle fileHandleForReadingAtPath：self.outputFilePath]; 
 
 NSAssert（outputFileHandle！= nil，@无法打开输出文件的句柄）; 
 
 @try {
 //寻找文件的开头
 [inputFileHandle seekToFileOffset：0]; 
 [outputFileHandle seekToFileOffset：0]; （（inputDataBuffer = [inputFileHandle readDataOfLength：1024]）！= nil）
 
 $ {
 [outputFileHandle writeData：[self.fileWrapper process：inputDataBuffer]]; 
 
 
 @catch（NSException * exception）{
 @throw; 
} 
 @finally {
 [inputFileHandle closeFile]; 
 [outputFileHandle closeFile]; 
 
 
 @catch（NSException * exception）{
 @throw; 
 
 
 
 
 $ b 
在尝试写入时出现以下异常： 
 
 $ b $ / b> 
 
 
 无法处理输入缓冲区（***  -  [NSConcreteFileHandle writeData：]：错误的文件描述符）
  
 
 
解决方案
需要更改 outputFileHandle  line ： 
 
 
  outputFileHandle = [NSFileHandle fileHandleForWritingAtPath：self.outputFilePath]; 
  
 
Are there good examples for doing file read/write in chunks with objective c? I am new to objective-c and iPhone API, here is the sample code that I wrote. Are there better ways to do it?
-(void) performFileOperation
{
    @try {

        NSFileHandle *inputFileHandle;
        NSFileHandle *outputFileHandle;

        //check whether the output file exist, if not create a new one.
        NSFileManager *morphedFileManager;

        outputFileManager = [NSFileManager defaultManager];

        if ([outputFileManager fileExistsAtPath: self.outputFilePath ] == NO)
        {
            NSLog (@"Output file does not exist, creating a new one");
            [outputFileManager createFileAtPath: self.outputFilePath
                                        contents: nil
                                      attributes: nil];
        }

        NSData *inputDataBuffer;

        inputFileHandle = [NSFileHandle fileHandleForReadingAtPath: self.inputFilePath];

        NSAssert( inputFileHandle != nil, @"Failed to open handle for input file" );

        outputFileHandle  = [NSFileHandle fileHandleForReadingAtPath: self.outputFilePath];

        NSAssert( outputFileHandle != nil, @"Failed to open handle for output file" );

        @try{
            // seek to the start of the file
            [inputFileHandle seekToFileOffset: 0];
            [outputFileHandle seekToFileOffset: 0];

            while( (inputDataBuffer = [inputFileHandle readDataOfLength: 1024]) != nil )
            {
                [outputFileHandle writeData: [self.fileWrapper process: inputDataBuffer]];
            }
        }
        @catch (NSException *exception) {
            @throw;
        }
        @finally {
            [inputFileHandle closeFile];
            [outputFileHandle closeFile];
        }        
    }
    @catch (NSException *exception) {
        @throw;
    }
}
I get the following exception while trying to write:
Failed to process input buffer ( *** -[NSConcreteFileHandle writeData:]: Bad file descriptor )

解决方案
Needs to change outputFileHandle line:
 outputFileHandle  = [NSFileHandle fileHandleForWritingAtPath: self.outputFilePath];


                        
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