validate method

  1. @override
String? validate(
  1. String? value
)
override

Validates the value and returns an error string if it fails, or null if it passes.

Implementation

@override
String? validate(String? value) {
  if (value == null || value.isEmpty) return null;
  // Standard ITU-T E.164 country code: starts with '+', then 1 to 3 (or 4) digits.
  if (!RegExp(r'^\+[1-9]\d{0,3}$').hasMatch(value)) {
    return message;
  }
  return null;
}