capturedGroups.swift

extension NSRegularExpression {
    func capturedGroups(forString string: String) -> [String?]? {
        let nsString = string as NSString
        let stringRange = NSRange(location:0, length: nsString.length)
        
        // Match
        guard let result = firstMatchInString(string, options: [], range: stringRange) else {
            return nil
        }
        
        // Iterate over captured groups
        var groups: [String?] = []
        for i in 0..<result.numberOfRanges {
            let range = result.rangeAtIndex(i)
            
            if range.location == NSNotFound {
                groups.append(nil)
            } else {
                let substring = nsString.substringWithRange(range)
                groups.append(substring)
            }
        }
        
        return groups
    }
}