toJson method
Creates a Map in Json format so data can be saved in SharedPreferences
Implementation
Map<String, dynamic> toJson() {
return {
'nickname': nickname,
'dateOfBirth': dateOfBirth?.toIso8601String(),
'sex': sex,
'levelOfStudies': levelOfStudies,
'testList': testList?.map((test) => test.toJson()).toList(),
'isSymbols1': isSymbols1,
};
}