Swift 닉네임 정규표현식

var str:String = "김ㄱㅋ11!"

var str1:String? = nil

//str1 = " "

var a = str1 ?? "1"

print("a = \(a)")

//str.vali

extension String {

    func validateNickname() -> Bool {

        let emailRegEx = "^[ㄱ-ㅎ가-힣a-zA-Z0-9]{2,20}$"

        let predicate = NSPredicate(format:"SELF MATCHES %@", emailRegEx)

        return predicate.evaluate(with: self)

    }

}