Creating tab delimited file in objective-c - iphone

Question

I found this snippet online to write, and then append data to a text file:
- (void)appendText:(NSString *)text toFile:(NSString *)filePath {
// NSFileHandle won't create the file for us, so we need to check to make sure it exists
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:filePath]) {
// the file doesn't exist yet, so we can just write out the text using the
// NSString convenience method
NSError *error = noErr;
BOOL success = [text writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
if (!success) {
// handle the error
NSLog(#"%#", error);
}
}
else {
// the file already exists, so we should append the text to the end
// get a handle to the file
NSFileHandle *fileHandle = [NSFileHandle fileHandleForWritingAtPath:filePath];
// move to the end of the file
[fileHandle seekToEndOfFile];
// convert the string to an NSData object
NSData *textData = [text dataUsingEncoding:NSUTF8StringEncoding];
// write the data to the end of the file
[fileHandle writeData:textData];
// clean up
[fileHandle closeFile];
}
}
This makes sense to me. I have a class that has 3 properties, of NSString, NSInteger, and NSString. When I try to use this method, I do this:
for (MyObject *ref in array) {
NSString *stringToFile = [NSString stringWithFormat:#"%#\t%i\t%#", ref.ChrID, ref.Position, ref.Sequence];
[self appendText:stringToFile toFile:filePath];
}
It doesn't look quite right. My data looks like this:
NSString *tab* NSInteger *single space* NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
NSStringNSString *tab* NSInteger newline
...
I'm not sure what is going on to make it look like this. When I NSLog the data, it looks fine. But something with the first line gets messed up, and then everything seems to be off. Any thoughts? Thanks.

Answer 1

There are several issues with the method appendText:
if the file does not exist, the first line is written with the NSString writeToFile method without the \n
following lines are written with the NSData writeData method
it's very inefficient to use a filemanager to check for existence, get a filehandle, seek to EOF and then write just one line, omitting the close too. And repeating this for every following line.
So better do it this way:
get the filehandle for writing, it will be created if it's not there yet
seek to EOF
do your loop with writeData for each line
close the file