validateCoordinateString function

String? Function(dynamic) validateCoordinateString({
  1. String? failMessage,
})

Returns error message if invalid, null if valid (validates combined "lat,lng" string)

Implementation

String? Function(dynamic) validateCoordinateString({String? failMessage}) {
  return (dynamic value) {
    if (value == null || value.isEmpty) return null;
    if (!isCoordinateString(value)) {
      return failMessage ?? 'Please enter valid coordinates (e.g., "40.7128,-74.0060" or "40.7128 -74.0060")';
    }
    return null;
  };
}