flatten function

Map<String, dynamic> flatten(Map<String, dynamic> target, { String delimiter = ".", bool safe = false, int? maxDepth, })

Flatten a nested Map into a single level map

If no delimiter is specified, will separate depth levels by ..

If you don't want to flatten arrays (with 0, 1,... indexes), use safe mode.

To avoid circular reference issues or huge calculations, you can specify the maxDepth the function will traverse.

Implementation

Map<String, dynamic> flatten(
  Map<String, dynamic> target, {
  String delimiter = ".",
  bool safe = false,
  int? maxDepth,
}) {
  final result = <String, dynamic>{};

  void step(
    Map<String, dynamic> obj, [
    String? previousKey,
    int currentDepth = 1,
  ]) {
    obj.forEach((key, value) {
      final newKey = previousKey != null ? "$previousKey$delimiter$key" : key;

      if (maxDepth != null && currentDepth >= maxDepth) {
        result[newKey] = value;
        return;
      }
      if (value is Map<String, dynamic>) {
        return step(value, newKey, currentDepth + 1);
      }
      if (value is List && !safe) {
        return step(
          _listToMap(value),
          newKey,
          currentDepth + 1,
        );
      }
      result[newKey] = value;
    });
  }

  step(target);

  return result;
}