Rename a file if file already exists

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];