Apple says that NSRegularExpression is based on the ICU Regular Expression library: https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSRegularExpression_Class/
The pattern syntax currently supported is that specified by ICU. The ICU regular expressions are described at http://userguide.icu-project.org/strings/regexp.
That page (on icu-project.org) claims that Named Capture Groups are now supported, using the same syntax as .NET Regular Expressions:
(?<name>...)Named capture group. The<angle brackets>are literal - they appear in the pattern.
I have written a program which gets a single match with multiple ranges which seem correct - though each range is returned twice (for reasons unknown) - but the only information I have is the range's index and its text range.
For example, the regex: ^(?<foo>foo)\.(?<bar>bar)\.(?<bar2>baz)$ with test string foo.bar.baz
Gives me these results:
Idx Start Length Text
0 0 11 foo.bar.baz
1 0 3 foo
2 4 3 bar
3 8 3 baz
Is there any way to know that "baz" came from the capture-group bar2?