Dart - Convert Map of objects fetched via HTTP REST-API - flutter

Question

For my Calendar i get the following data as JSON from the Backend (*JAVA-Type = Map<LocalDate, List<Event>>):
{
"2022-05-28": [
{
"id": 2,
"title": "Multi day Event",
"fromDate": "2022-05-27T12:22:03.873569",
"toDate": "2022-05-28T11:22:03.873569",
"room": {
"id": 1,
"name": "TestRoom",
},
"user": {
"id": 1,
"name": "Andi",
"city": "",
"email": "test#gmail.com",
},
"eventType": "sozial"
}
],
"2022-05-27": [
{
"id": 2,
"title": "Multi day Event",
"fromDate": "2022-05-27T12:22:03.873569",
"toDate": "2022-05-28T11:22:03.873569",
"room": {
"id": 1,
"name": "TestRoom",
},
"user": {
"id": 1,
"name": "Andi",
"city": "",
"email": "test#gmail.com",
},
"eventType": "sozial"
},
{
"id": 1,
"title": "Testevent",
"fromDate": "2022-05-27T11:21:04.573754",
"toDate": "2022-05-27T12:21:04.573754",
"room": {
"id": 1,
"name": "TestRoom",
},
"user": {
"id": 1,
"name": "Andi",
"city": "",
"email": "test#gmail.com",
},
"eventType": "normal"
}
],
}
My Event Class looks like:
Class Event {
int id;
String title;
DateTime fromDate;
DateTime toDate;
Room room;
User user;
String eventType;
}
Now i need the same structure i had in the Backend (Map<DateTime, <List<Event>>) for my Calendar widget and i have no real clue on how to do it. I know how to convert json data into an object if i get a list of an object, but how can i store the date as key of the resulting map?
My code by now:
Future<Map<DateTime, List<Event>>> getEvents(DateTime _fromDate, DateTime
_endDate) async {
String _from = _fromDate.toString().split('.').first;
String _end = _endDate.toString().split('.').first;
final response = await get('${_url}calendar/events/$_from/$_end',
headers: {HttpHeaders.authorizationHeader: 'Bearer $_bearer'});
if (response.status.hasError) {
return Future.error('${response.statusText}');
} else {
final parsed = jsonDecode(response.body);
return parsed;
}
}

Answer 1

You need to do something like that:
var json = {...}; // <-- json obj
// method to parse data to map with list Event
dynamic fromJson(Map<String, dynamic> json){
var map = new Map();
json.keys.forEach((key){
// key is the date
map[key] = json[key].map((e) => Event.fromJson(e)).toList(); // <- need to create a method fromJson in your Event class
});
return map;
}
(...)
class Event {
int id;
String title;
DateTime fromDate;
DateTime toDate;
Room room;
User user;
String eventType;
fromJson(Map<String, dynamic> json) => Event(...); // <- parse json to Event class
}