Hey,

I have a problem with a regular expression. I am trying to match an image URL in a string with the following pattern:

let imageName = "img/background.jpg"
let pattern = #"url\(['"]?(..\/)*(img\/background.jpg)['"]?\);"#

Trying to iterate through the matches

func findImageUrls(in: String, using pattern: String) -> [String] {
    do {
        let regex = try NSRegularExpression(pattern: pattern, options: [])
        print(regex.pattern)
        let stringRange = NSRange(location: 0, length: `in`.utf8.count)
        let matches = regex.matches(in: `in`, range: stringRange)
        var result: [[String]] = []
        for match in matches {
            var groups: [String] = []
            for rangeIndex in 1 ..< match.numberOfRanges {
                groups.append((`in` as NSString).substring(with: match.range(at: rangeIndex)))
            }
            if !groups.isEmpty {
                result.append(groups)
            }
        }
        return result.flatMap { $0 }

    } catch let error {
        print(error)
        return []
    }
}

produces a crash. The reason is that match.range(at: rangeIndex) produces an invalid range: {9223372036854775807, 0}.

I verified that the regex is working on Regex101 and read Paul's article on raw strings.

I have a feeling something about the escaping is not right :) Anyone has an idea what's wrong?

Thanks!

Cordt