writeToFile in OSX, appending to the file?

Question

I need to write some data from time to time to a file, appending to it.

Right now I have:

BOOL ok = [[NSString stringWithFormat:@"%f",raw] writeToFile:path atomically:YES encoding:NSUnicodeStringEncoding error:&error];

How could I append to the end of the file the new contents of raw?

Answer 1

Here is an NSString category method that will append the receiver to the specified path with the specified encoding (normally NSUTF8StringEncoding).

- (BOOL) appendToFile:(NSString *)path encoding:(NSStringEncoding)enc;
{
    BOOL result = YES;
    NSFileHandle* fh = [NSFileHandle fileHandleForWritingAtPath:path];
    if ( !fh ) {
        [[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil];
        fh = [NSFileHandle fileHandleForWritingAtPath:path];
    }
    if ( !fh ) return NO;
    @try {
        [fh seekToEndOfFile];
        [fh writeData:[self dataUsingEncoding:enc]];
    }
    @catch (NSException * e) {
        result = NO;
    }
    [fh closeFile];
    return result;
}

Answer 2

One method would be to obtain a NSFileHandle using fileHandleForWritingAtPath: method, converting your NSString to NSData and then calling writeData: on your NSFileHandle after moving the file pointer to the end of the file.

Answer 3

Li'l edit to Peter N Lewis Answer:

- (BOOL) appendToFile:(NSString *)path encoding:(NSStringEncoding)enc;
{
    BOOL result = YES;
    NSFileHandle* fh = [NSFileHandle fileHandleForWritingAtPath:path];
    if ( !fh ) {
        [[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil];
        fh = [NSFileHandle fileHandleForWritingAtPath:path];
    }
    if ( !fh ) return NO;
    @try {
        [fh seekToEndOfFile];
        [fh writeData:[strcontent dataUsingEncoding:enc]];
    }
    @catch (NSException * e) {
        result = NO;
    }
    [fh closeFile];
    return result;
}

Call Where ever you want

 [self appendToFile:fileName encoding:NSUTF8StringEncoding];

Answer 4

strcontent may be self when you put this method to a Catagory of NSString.