LengthBetween static method

String? Function(String? value)? LengthBetween(int min, int max, { String errorMessage = 'Field Should be atleast *min_len* and at most *max_len* characters long', String? next(String value)?, })

Returns a validator that checks if a string's length lies between the values provided

Arguments :

• min : The minimum length of the string.
• max : The maximum length of the string.
• errorMessage : The error message to return if the string is not at least a certain length.
• next : A validator to run after this validator.

Usage :

TextFormField(
validator: Validators.LengthBetween(3,11),
),

Implementation

static String? Function(String? value)? LengthBetween(
  int min,
  int max, {
  String errorMessage =
      'Field Should be atleast *min_len* and at most *max_len* characters long',
  String? Function(String value)? next,
}) {
  assert(min <= max, 'min cannot be greater than max');
  if (errorMessage.contains('*min_len*')) {
    errorMessage = errorMessage.replaceAll('*min_len*', min.toString());
  }
  if (errorMessage.contains('*max_len*')) {
    errorMessage = errorMessage.replaceAll('*max_len*', max.toString());
  }
  return (value) {
    if (value == null || value.trim().isEmpty) {
      return null;
    }

    if (value.length < min) {
      return errorMessage;
    }

    if (value.length > max) {
      return errorMessage;
    }

    if (next != null) {
      return next(value);
    }

    return null;
  };
}