/// a struct description a people /// class People { People({ required this.name, this.age = 10, required this.sex, this.children = const <People>[], this.parents = const <String, People>{}, }); factory People.fromJson(final Map<String, dynamic> json) => People( name: getValueFromJsonOrNull<String>(json, 'name'), age: getValueFromJsonOrDefault<int>(json, 'age', 10), sex: getValueFromJsonOrNull<String>(json, 'sex'), children: getListFromJson<People>(json, 'children'), parents: getMapFromJson<People>(json, 'parents'), ); final String? name; final int age; final String? sex; final List<People> children; final Map<String, People> parents; Map<String, dynamic> toJson() => <String, dynamic>{ 'name': name, 'age': age, 'sex': sex, 'children': getJsonFromList(children), 'parents': getJsonFromMap(parents), }; }