checkPassword function
Implementation
String? checkPassword(String? input){
if(input==null)return "Please enter Password";
if (!RegExp(password12Pattern).hasMatch(input)) {
return "Password must be at least 12 characters";}
if (!input.contains(RegExp(r'[a-z]'))){
return "Password must contain a lower case letter";}
if (!input.contains(RegExp(r'[A-Z]'))){
return "Password must contain a upper case letter";}
if (!input.contains(RegExp(r'[0-9]'))){
return "Password must contain a number";}
if (!input.contains(RegExp(r'[!@#\$%^&*~(),.?":{}|<>]'))){
return "Password must contain a special letter";}
return null;
}