PCRE2RegularExpression

PCRE2RegularExpression is an Objective-C wrapper for the PCRE2 regular expression library. PCRE2RegularExpression aims to be a drop-in replacement for NSRegularExpression. In many cases all you need to do is replace references to NSRegularExpression with PCRE2RegularExpression in your code.

PCRE2RegularExpression is fully Unicode safe.

Background

Although Cocoa provides built-in support for regular expressions through the NSRegularExpression class, NSRegularExpression only supports the ICU regular expression pattern syntax, which lacks many features found in more powerful engines such as PCRE/PCRE2.

I created this project to support my own needs while developing the Scribe for Xcode plugin, and it only implements the subset of functionality that I needed. However, since Scribe relies heavily on complicated regular expressions, I believe this code will be immediately useful to most people, and can serve as a foundation for others.

Usage

Use PCRE2RegularExpression just like you would NSRegularExpression:

PCRE2RegularExpression *re;
re = [PCRE2RegularExpression regularExpressionWithPattern:@"foo"
                                                  options:NSRegularExpressionCaseInsensitive 
                                                    error:&error];
[re enumerateMatchesInString:myString 
                     options:NSRegularExpressionCaseInsensitive 
                       range:myRange
                  usingBlock:^(NSTextCheckingResult * _Nullable result, NSMatchingFlags flags, BOOL * _Nonnull stop) {
// ...
}];

Harness the power of PCRE2 features like named capture groups:

NSString *pat = @"(a)(?P<mygroup>b+)(c)";
PCRE2RegularExpression *re;
re = [PCRE2RegularExpression regularExpressionWithPattern:pat 
                                                  options:NSRegularExpressionCaseInsensitive 
                                                    error:&error];
NSString *s = @"abbbc";
NSArray<NSTextCheckingResult *> *res = [re matchesInString:s options:0 range:NSMakeRange(0, s.length)];
NSRange rangeOf_bbb = [re rangeOfNamedCapture:@"mygroup" inTextCheckingResult:res[0]];

Installation

Install PCRE2 on your system using Homebrew:

brew install pcre2

The above installs into something like /usr/local/Cellar/pcre2/10.20.

In your Xcode project, under Build Settings add /usr/local/Cellar/pcre2/10.20/include to the Header Search Paths.

In your target, under the General tab, press + under Linked Frameworks and Libraries. Click "Other" and add /usr/local/Cellar/pcre2/10.20/lib/libpcre2-16.a. We're using the -16 version which uses 16-bit characters.

Finally, add PCRE2RegularExpression.m and PCRE2RegularExpression.h to your project.

Possible Future Enhancements

1. Improved code optimizations.
2. Expose more PCRE2-specific functionality through new APIs.
3. Support a fuller subset of the NSRegularExpression API.

Acknowledgments

This project was inspired by cmkliger's PCRERegex. In comparison to PCRERegex, this project uses PCRE2 (vs PCRE1), and has Unicode support.

License

MIT License.