Fast Validator

A flutter package to validate text fields, date fields or any data fastly. The package contains a list of built in commonly used validators. You can also add custom validators for your needs.

Screenshots

Validating an email id

Validating the email id "[email protected]" (valid)

Validating the email id "[email protected]" (invalid because contains '..')

Usage

Import it

import 'package:fast_validator/fast_validator.dart';

Use the default validator function to validate anything.

ValidationResult result = FastValidator.validate(text,fieldName: 'Username',validators: [FastRequiredValidation()]);

The ValidationResult/ValidationAllResult class will contain the below details.

Variable	Type	Description
valid	bool	indicates whether the given data have passed all the given validations
errorMessage	String	The error message after validation. This will be null if the data is valid
allErrorMessage	List	list of errors after validating all validators given to the validate function (only available with FastValidator.validateAll())
type	ResultType	An enum indicating the validation result status, like valid, invalid, validWithNoValue. ValidWithNoValue indicates the filed was valid but did not contain any data. This can be useful if you are trying to validate any filed which is not a required one
result	Same as the type of input data	the same data given as input to the validation function

The FastValidator.validate function has three arguments. First parameter is the data to be validated. This can be of any type such as String, int, List etc.

The fieldName is the name of the filed which you are validating. This is just to make a meaningful validation message. For example if you give the filedName as 'Username', then the default validation error message will be 'Username is required'. If you provide fieldName as 'XYZ', then the default validation error message will be 'XYZ is required'.

The validators parameter is the list of validations to be done on the given data. These validations are done in the order in which they are kept in the list. For example, if you give the list as validators: [FastRequiredValidation(), FastEmailValidation()], then the FastRequiredValidation() validation will be executed first. If that validation is passed then the FastEmailValidation() will be executed.

Use

  ValidationResult result = FastValidator.validate(
  text,
  fieldName: 'Sample field name',
  validators: [FastRequiredValidation(), FastMaxLengthValidation(maxLength: 12)],
);

if you want to get the first error at which the validation failed. FastValidator.validate() will be returning the error result immediately if any of the validations in the list fails. The rest of the validations in the list will not be executed. Hence the error message will be a 'String'.

Use

    ValidationAllResult result = FastValidator.validateAll(
  text,
  fieldName: 'Sample field name',
  validators: [FastRequiredValidation(), FastMinLengthValidation(minLength: 12)],
);

if you want to get the all the errors from the list of validations given. FastValidator.validateAll() function will be returning a list of errors after executing all the given validations in the list.

Build in validators

The below given are the ready-made validators you can use. Most of the validators will have optional arguments to customize the validation.

Validator	Description
FastRequiredValidation()	used to do required validation on a filed. Null and empty fields are also considered as invalid
FastMinLengthValidation()	used to validate minimum length of a string
FastMaxLengthValidation()	used to validate maximum length of a string
FastExactLengthValidation()	used to validate exact length of a string
FastMinValueValidation()	used to validate minimum value of a number
FastMaxValueValidation()	used to validate maximum value of a number
FastExactValueValidation()	used to validate exact value of given data
FastTypeValidation()	used to validate the datatype of given data
FastEmailValidation()	used to validate an email
FastUrlValidation()	used to validate an URL
FastDigitsOnlyValidation()	used to validate whether a string contains numbers alone
FastAlphabetsOnlyValidation()	used to validate whether a string contains alphabets alone
FastAlphaNumericOnlyValidation()	used to validate whether a string contains alphabets and numbers alone
FastAllowedCharactersValidation()	used to validate whether a string contains the allowed characters alone
FastRegexValidation()	used to validate a String against a RegExp
FastPasswordValidation()	used to validate a password field
FastDateValidation()	used to validate a date field
FastCreditCardValidation()	used to validate a credit card number using Luhn's algorithm
FastGSTNumberValidation()	used to validate a GST number
FastPhoneNumberValidation()	used to validate a phone number

Custom validator

You can create your own validators and can even use them along with the build in validations. To create a custom validator, create a class and extend it with FastValidation class as shown in the below example.

class MyCustomValidator extends FastValidation {
final String? errorMessage; // Optional error message
MyCustomValidator({this.errorMessage});

@override
validate<T>(T toValidate, String? fieldName) {
String? error;
bool valid = true;
ResultType outputType = ResultType.valid; // setting the default value to valid

// the main validation  condition. In this example we are just checking whether the input data is a String or not.
    if (toValidate.runtimeType != String) {  
      error = errorMessage ?? 'This filed must be a string';
      valid = false;
      outputType = ResultType.invalid;
    }

    return ValidationResult<T>(
      errorMessage: error,
      type: outputType,
      valid: valid,
      result: toValidate,
    );
}
}

And now you can use this in the FastValidator.validate() function as shown below.

    ValidationResult result = FastValidator.validate(
      50,
      fieldName: null,
      validators: [MyCustomValidator()],
    );

    debugPrint('Result: ${result.result}');
    debugPrint('Valid: ${result.valid}');
    debugPrint('Type: ${result.type}');
    debugPrint('ErrorMsg: ${result.errorMessage}');

Usage in TextFormField

You can use the FastValidator.validate() function directly with the TextFormFiled widget as shown below.

    TextFormField(
    controller: textController,
    decoration: const InputDecoration(
    contentPadding: EdgeInsets.symmetric(horizontal: 6, vertical: 0),
    border: OutlineInputBorder(borderSide: BorderSide(width: 3, color: Colors.green)),
    ),
    validator: (String? text) {
    ValidationResult result = FastValidator.validate(text?.trim(),
    fieldName: 'Personal email', validators: [FastRequiredValidation(), FastEmailValidation()]);

    return result.errorMessage;
    },
    )

Feel free to contribute and support.

Contributors 🤝

Big thanks go to these wonderful people:

Author: Christo Pananjickal

Package on pub.dev

fast_validator