alphanum static method

String? alphanum(
  1. String? value
)

Implementation

static String? alphanum(String? value) {
  if (value == null || value.isEmpty) {
    return 'This field is required';
  }
  if (!RegExp(r'^[a-zA-Z0-9]+$').hasMatch(value)) {
    return 'Only letters and numbers are allowed';
  }
  return null;
}