validateUsername static method

String? validateUsername(
  1. String? value
)

Implementation

static String? validateUsername(String? value) {
  if (value == null || value.isEmpty) {
    return 'Username is required';
  } else if (value.length < 4) {
    return 'Username must be at least 4 characters';
  } else if (!RegExp(r'^[a-zA-Z0-9_]+$').hasMatch(value)) {
    return 'Username can only contain letters, numbers, and underscores';
  }
  return null;
}