@omochimetaru こんなメソッドで判定してますね
func isValidEmailFormat(string: String) -> Bool { let emailReg = "[a-zA-Z0-9._%+-/:~$^()&!']+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}" let predicateMail = NSPredicate(format:"SELF MATCHES %@", emailReg) return predicateMail.evaluate(with: string) } (edited)