[SOLVED] NSString hasPrefix: vs hasSuffix: which is less expensive?

NSString hasPrefix: vs hasSuffix: which is less expensive?

In my project I need to have a list of predefined prefix or suffix for string items, it can be either prefix or suffix, so that I can go through the items and check the prefix or suffix of each item, just wondering which is less expensive? It feels like hasPrefix: is less expensive but I don't have any reference to support this.

Thanks

Solution

NSString is "toll-free bridged" to CFStringRef, so you can check the implementation in CFString.c.

The relevant functions are CFStringHasPrefix() and CFStringHasSuffix(), which call CFStringFindWithOptionsAndLocale() without or with the kCFCompareBackwards flag.

As I understand the code, this flag has no influence on the performance, only some loop variables are initialized differently.

(But the general "disclaimer" applies here as well: You should profile your application and check if the prefix/suffix check is a performance bottleneck at all. If not, choose whatever is more logical or easier to maintain.)