I created a string validator and I need to add these things to check in my input strings. How do I do it?

• Minimum of 6 characters.
• Maximum of 15 characters.
• Digits should not be adjacent to one another like:
  • invalid: bq34
  • valid: b3q4
• Minimum 1 Upper case.
• Minimum 1 lowercase.
• Minimum 2 Numeric Numbers.
• Each character should occur a maximum of once.
• Minimum 1 Special Character.
• Common Allow Character ( $, %, >).

CodePudding user response：

you can check the number of characters of a String using .length(), for 1 upper case letter and 1 lower case letter you should use pattern like this

this is for password validation.

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


RegExp regExp = new RegExp(pattern);

Explanation:

(?=.*[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

(?=.?[!@#$&~]) // should contain at least one Special character

.{8,} // Must be at least 8 characters in length

 @override
  String validator(String value) {
    if (value.isEmpty) {
      return 'Password can\'t be empty';
    } else if (value.isNotEmpty) {
        String  pattern = r'^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9])(?=.*?[!@#\$&*~]).{8,}$';


      RegExp regExp = new RegExp(pattern);

      bool passvalid =
          regExp.hasMatch(value);
      return passvalid ? null : "Invalid Password";
    }
  }

CodePudding user response：

Try using this package it has all the validations you are asking for

https://pub.dev/packages/form_field_validator/

This is just an example how to use this package with textfield or textformfield.

    final passwordValidator = MultiValidator([  
    RequiredValidator(errorText: 'password is required'),  
    MinLengthValidator(8, errorText: 'password must be at least 8 digits long'),  
    PatternValidator(r'(?=.*?[#?!@$%^&*-])', errorText: 'passwords must have at least one special character')  
 ]);  
  
  String password;  
  
  Form(  
    key: _formKey,  
    child: Column(children: [  
      TextFormField(  
        obscureText: true,  
        onChanged: (val) => password = val,  
        // assign the the multi validator to the TextFormField validator  
        validator: passwordValidator,  
      ),  
  
      // using the match validator to confirm password  
      TextFormField(  
        validator: (val) => MatchValidator(errorText: 'passwords do not match').validateMatch(val, password),  
      )  
    ]),  
  );