optionalString method

String? optionalString(
  1. String key, {
  2. String? fallback,
})

Optional String: returns fallback when the key is absent, but still records an error when the key is present with a non-string value (bad data is a real problem; a missing optional field is not). Audited: 2026-06-12 11:26 EDT

Implementation

String? optionalString(String key, {String? fallback}) {
  final Object? v = _map[key];
  if (v == null) return fallback;
  if (v is String) return v;
  _typeError(key, v, 'string');
  return fallback;
}