Firestore collection map to list - flutter

Question

Hi I need to retrieve all documents from firestore collection with this:
EventList<Event>testdata(QuerySnapshot snapshot) {
return snapshot.docs.map((data) => EventList<Event>(events: {
data['date']: [
Event(
date: data['date'], title: data['name'], icon: Icon(
Icons.block,
color: Colors.red[200],
size: 30,
)),
]
})).toList();
}
Stream<EventList<Event>> get caldendardata {
return events.snapshots().map(testdata);
}
but i get this error: A value of type 'List<EventList<Event>>' can't be returned from the method 'testdata' because it has a return type of 'EventList<Event>'.
The Firestore :
I'm using this package to add calendar to my app it requires the event on the calendar to be {EventList<Event>? markedDatesMap} .
EventList form the package:
class EventList<T> {
Map<DateTime, List<T>> events;
EventList({
required this.events,
});
void add(DateTime date, T event) {
final eventsOfDate = events[date];
if (eventsOfDate == null)
events[date] = [event];
else
eventsOfDate.add(event);
}
void addAll(DateTime date, List<T> events) {
final eventsOfDate = this.events[date];
if (eventsOfDate == null)
this.events[date] = events;
else
eventsOfDate.addAll(events);
}
bool remove(DateTime date, T event) {
final eventsOfDate = events[date];
return eventsOfDate != null ? eventsOfDate.remove(event) : false;
}
List<T> removeAll(DateTime date) {
return events.remove(date) ?? [];
}
void clear() {
events.clear();
}
List<T> getEvents(DateTime date) {
return events[date] ?? [];
}
}
Event form the package:
class Event implements EventInterface {
final DateTime date;
final String? title;
final Widget? icon;
final Widget? dot;
final int? id;
Event({
this.id,
required this.date,
this.title,
this.icon,
this.dot,
});
#override
bool operator ==(dynamic other) {
return this.date == other.date &&
this.title == other.title &&
this.icon == other.icon &&
this.dot == other.dot &&
this.id == other.id;
}
#override
int get hashCode => hashValues(date, title, icon, id);
#override
DateTime getDate() {
return date;
}
#override
int? getId() {
return id;
}
#override
Widget? getDot() {
return dot;
}
#override
Widget? getIcon() {
return icon;
}
#override
String? getTitle() {
return title;
}
}
abstract class EventInterface {
DateTime getDate();
String? getTitle();
Widget? getIcon();
Widget? getDot();
int? getId();
}
I would appreciate a little help here.
Thank you in advance

Answer 1

map returns a List. That's why you have a List<EventList>.
I believe you are trying to flatten the list so that you instead have a single EventList with all of the events. One way to accomplish this is to use fold.
Here is an example that you should be able to apply to your code. One could paste this into Dartpad to quickly see how it works:
class Event {
const Event(this.id);
final int id;
}
class EventList {
const EventList({required this.events});
final List<Event> events;
}
class FirebaseData {
const FirebaseData(this.docs);
final List<Event> docs;
}
void main() {
// Simulating your data stream
final FirebaseData snapshot = FirebaseData(List.generate(5, (index) => Event(index)));
// What you are returning from your code currently
final List<EventList> eventListList =
snapshot.docs.map((data) => EventList(events: [data])).toList();
// What you actually want to return from your code
final EventList eventList = eventListList.fold(EventList(events: []),
(previousValue, element) => EventList(events: previousValue.events..addAll(element.events)));
print(eventList.events);
}

Answer 2

When performing toList you getting a List<EventList<Event>> each EventList with one event.
I think you want to get a List<Map> from Firestore to later build your class.
You can achieve that with a code like this.
EventList<Event>testdata(QuerySnapshot snapshot) {
//Get all data
final List<Map> eventListMap = snapshot.docs.map((data) => {
data['date']: [
Event(
date: data['date'], title: data['name'], icon: Icon(
Icons.block,
color: Colors.red[200],
size: 30,
)),
]
}).toList();
//Join to single Map, it should not contain repeated keys (date) as one of them would be lost
final Map eventsMap = eventsData.fold({},(map1, map2) => map1..addAll(map2));
//Return your class
return EventList<Event>(events: eventsMap);
}
Stream<EventList<Event>> get caldendardata {
return events.snapshots().map(testdata);
}
I did not try it and you can rename or change anything.