How to apply this regex to NSRegularExpression?

\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b

https://www.regular-expressions.info/email.html

How do I apply the regex above to an NSRegularExpression in Swift? I get a SIGABRT error when I run this code.

func validEmail(from input: String) -> String? {
    do {
        let regex = try NSRegularExpression(pattern: #"\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b"#,
                                            options: .caseInsensitive)
        let range = NSRange(location: 0, length: input.utf16.count)
        let matches = regex.matches(in: input, options: [], range: range)
        
        if let match = matches.first {
            let matchedRange = match.range(at: 1)
            if let swiftRange = Range(matchedRange, in: input) {
                return String(input[swiftRange])
            }
        }
    } catch {
        print(error)
    }
    return nil
}

let email = "a@a.com"
print(validEmail(from: email) ?? "invalid email")

>Solution :

You can simply use string range(of:) and pass .regularExpression to options. To match lowercased as well you just need to add a-z to your regex:

func validEmail(from input: String) -> String? {
    guard let range = input.range(of:  #"\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}\b"#, options: .regularExpression) else { return nil }
    return String(input[range])
}

let email = "a@a.com"
print(validEmail(from: email) ?? "invalid email")  // a@a.com

To just literally fix the error you need to pass zero to the range:

match.range(at: 0)