File Read / Write operation

//Clear content of file

 paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

 NSLog(@"readFile Path : %@ ",paths);

 documentsDirectory = [paths objectAtIndex:0];

 appFile = [documentsDirectory stringByAppendingPathComponent:@"File.txt"];

 fileManager=[NSFileManager defaultManager];

 NSFileHandle *file;                  

 file = [NSFileHandle fileHandleForUpdatingAtPath: appFile];

                    

 if (file == nil)

      NSLog(@"Failed to open file");

 [file truncateFileAtOffset:0];                    

 [file closeFile];

//Method to invoke writeFile

[(AppDelegate *)[[UIApplication sharedApplication]delegate]

                     writeFile:@"DeptListFile.txt" data:newFileString]; 

// Method to Write in file

-(void)writeFile:(NSString *)fileName data:(id)data {

    

    paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSLog(@"writeFile Path : %@ ",paths);

    

    documentsDirectory = [paths objectAtIndex:0];

    NSLog(@"documentsDirectory : %@ ",documentsDirectory);

    

    appFile = [documentsDirectory stringByAppendingPathComponent:fileName];

    NSLog(@"documentsDirectory : %@ ",documentsDirectory);

    

    NSError *error=NULL;

    fileManager=[NSFileManager defaultManager];

    

    if ([fileManager fileExistsAtPath:appFile]) {

        

        NSString *fileString=[NSString stringWithContentsOfFile:appFile 

                             encoding:NSUTF8StringEncoding error:&error];

        

        data=[data stringByAppendingFormat:@"\n%@",fileString];

        

        [data writeToFile:appFile atomically:YES encoding:NSUTF8StringEncoding error:&error];

    }

    else {

        [data writeToFile:appFile atomically:YES encoding:NSUTF8StringEncoding error:&error];

    }

    

    if (error != NULL) {

        //Check Error Here. if any.

    }

}

// Code to read from file

NSString *fileText = [self readFile:@"File.txt"];

NSLog(@"File content : %@ ",fileText);

// Read from file

-(NSString *)readFile:(NSString *)fileName {

    paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSLog(@"readFile Path : %@ ",paths);

    

    documentsDirectory = [paths objectAtIndex:0];

    NSLog(@"documentsDirectory : %@ ",documentsDirectory);

    

    appFile = [documentsDirectory stringByAppendingPathComponent:fileName];

    NSLog(@"appFile : %@ ",appFile);

    

    fileManager=[NSFileManager defaultManager];

    

    if ([fileManager fileExistsAtPath:appFile]) {

        NSError *error= NULL;

        id resultData=[NSString stringWithContentsOfFile:appFile encoding:NSUTF8StringEncoding 

                      error:&error];

        

        if (error == NULL) {

            return resultData;

        }

    }

    

    return NULL;

}