Validate.swift

private func validate(_ emailString: String) -> String? {
    let dataDetector = try! NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
        
    // Finding matches in string
    let range = NSRange(emailString.startIndex..<emailString.endIndex, in: emailString)
    guard let match = dataDetector.firstMatch(in: emailString, options: .anchored, range: range) else { return nil }
    guard let url = match.url else { return nil }
        
    // Extracting email from the matched url
    let absoluteString = url.absoluteString
    guard let index = absoluteString.range(of: "mailto:") else { return nil }
    return String(url.absoluteString.suffix(from: index.upperBound))
}