fromJson static method

StateGraph? fromJson(dynamic value)

Returns a new StateGraph instance and imports its values from value if it's a Map, null otherwise.

Implementation

// ignore: prefer_constructors_over_static_methods
static StateGraph? fromJson(dynamic value) {
  if (value is Map) {
    final json = value.cast<String, dynamic>();

    // Ensure that the map contains the required keys.
    // Note 1: the values aren't checked for validity beyond being non-null.
    // Note 2: this code is stripped in release mode!
    assert(() {
      requiredKeys.forEach((key) {
        assert(json.containsKey(key), 'Required key "StateGraph[$key]" is missing from JSON.');
        assert(json[key] != null, 'Required key "StateGraph[$key]" has a null value in JSON.');
      });
      return true;
    }());

    return StateGraph(
      initial: mapValueOfType<String>(json, r'initial'),
      live: mapValueOfType<String>(json, r'live'),
      states: json[r'states'] is Iterable
          ? (json[r'states'] as Iterable).cast<String>().toList(growable: false)
          : const [],
      transitions: json[r'transitions'] == null
        ? const {}
          : (json[r'transitions'] as Map).map((k, v) => MapEntry(k as String, v == null ? const <String>[] : (v as List).cast<String>().toList(growable: false))),
    );
  }
  return null;
}