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How do I use NSRange with this NSString?
productID = @"com.sortitapps.themes.pink.book";

partialID = @"com.sortitapps.themes.pink.";

NSString *str = @"com.sortitapps.themes.pink.book";
NSUInteger dot = [str rangeOfString:@"." options:NSBackwardsSearch].location;

NSString *newStr =
   [str stringByReplacingCharactersInRange:NSMakeRange(dot+1, [str length]-dot-1)
                                withString:@"something_else"];

[productID stringByDeletingPathExtension];