Rename a file if file already exists - ios

Question

What is the best way in objective-c to rename a file if a file with a same name exists.
Ideally, I would like to name untitled.png to untitled-1.png if a file named untitled.png already exists.
I have included my solution below as an answer, but I think there should be a better way (built-in function) to do it.
My solution is not thread-safe, and susceptible to race conditions.

Answer 1

The following function returns the next available filename:
//returns next available unique filename (with suffix appended)
- (NSString*) getNextAvailableFileName:(NSString*)filePath suffix:(NSString*)suffix
{
NSFileManager* fm = [NSFileManager defaultManager];
if ([fm fileExistsAtPath:[NSString stringWithFormat:#"%#.%#",filePath,suffix]]) {
int maxIterations = 999;
for (int numDuplicates = 1; numDuplicates < maxIterations; numDuplicates++)
{
NSString* testPath = [NSString stringWithFormat:#"%#-%d.%#",filePath,numDuplicates,suffix];
if (![fm fileExistsAtPath:testPath])
{
return testPath;
}
}
}
return [NSString stringWithFormat:#"%#.%#",filePath,suffix];
}
An example calling function is as follows:
//See" http://stackoverflow.com/questions/1269214/how-to-save-an-image-that-is-returned-by-uiimagepickerview-controller
// Get the image from the result
UIImage* image = [info valueForKey:#"UIImagePickerControllerOriginalImage"];
// Get the data for the image as a PNG
NSData* imageData = UIImagePNGRepresentation(image);
// Give a name to the file
NSString* imageName = #"image";
NSString* suffix = #"png";
// Now we get the full path to the file
NSString* filePath = [currentDirectory stringByAppendingPathComponent:imageName];
//If file already exists, append unique suffix to file name
NSString* fullPathToFile = [self getNextAvailableFileName:filePath suffix:suffix];
// and then we write it out
[imageData writeToFile:fullPathToFile atomically:NO];