How to handle TextField validation in password in Flutter

Question

I created a login page and I need to add these things to my password. How do I do it with validation alert message?

• Minimum 1 Upper case

Answer 1

Your regular expression should look like:

r'^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[!@#\$&*~]).{8,}$

Here is an explanation:

r'^
  (?=.*[A-Z])       // should contain at least one upper case
  (?=.*[a-z])       // should contain at least one lower case
  (?=.*?[0-9])          // should contain at least one digit
 (?=.*?[!@#\$&*~]).{8,}  // should contain at least one Special character
$

Match above expression with your password string.Using this method-

String validatePassword(String value) {
    Pattern pattern =
        r'^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[!@#\$&*~]).{8,}$';
    RegExp regex = new RegExp(pattern);
    print(value);
    if (value.isEmpty) {
      return 'Please enter password';
    } else {
      if (!regex.hasMatch(value))
        return 'Enter valid password';
      else
        return null;
    }
  }