decodeList method

List<T> decodeList(String? jsonString, { List<String>? nodeRoute, })

Parses jsonString and invokes fromJson for every entry in the payload when the input is a JSON array of objects. When nodeRoute is provided the decoded payload must be a JSON object and its nested value is resolved by following the segments in nodeRoute. Throws a FormatException when the resulting payload is not a JSON array, when an entry is not a JSON object, or when parsing fails.

Implementation

List<T> decodeList(
  String? jsonString, {
  List<String>? nodeRoute,
}) {
  try {
    if (jsonString == null || jsonString.trim().isEmpty) {
      return <T>[];
    }

    final dynamic decoded = jsonDecode(jsonString);
    if (decoded == null) {
      return <T>[];
    }
    dynamic payload = decoded;

    if (nodeRoute != null && nodeRoute.isNotEmpty) {
      if (payload is! Map) {
        throw const FormatException('Expected a JSON object.');
      }
      payload = Map<String, dynamic>.from(payload);

      for (final segment in nodeRoute) {
        if (payload is! Map<String, dynamic>) {
          throw const FormatException('Expected a JSON object.');
        }
        if (!payload.containsKey(segment)) {
          return <T>[];
        }
        final dynamic next = payload[segment];
        if (next == null) {
          return <T>[];
        }
        if (next is Map) {
          payload = Map<String, dynamic>.from(next);
        } else {
          payload = next;
        }
      }
    }

    if (payload == null) {
      return <T>[];
    }
    if (payload is Map) {
      throw const FormatException('Expected a JSON array.');
    }
    if (payload is! List) {
      throw const FormatException('Expected a JSON array.');
    }

    return List<T>.generate(payload.length, (index) {
      final dynamic entry = payload[index];
      if (entry is! Map<String, dynamic>) {
        throw const FormatException('Expected a JSON object.');
      }
      final map = Map<String, dynamic>.from(entry);
      return _fromJson(map);
    }, growable: true);
  } on FormatException catch (error) {
    throw FormatException('Failed to parse JSON: ${error.message}');
  } catch (error) {
    throw FormatException('Failed to parse JSON: $error');
  }
}