CODEWITHSUNDEEP
flutterdart
Kamlesh
Kamlesh

Reputation: 6135

How to add new data into Future<dynamic> in dart / flutter?

I am developing a chat system in mobile application using Flutter / Dart.

I have fetched a user's message records from server by API and received result as Future<dynamic>. This result has list of chat data. If I pass it to FutureBuilder widget. It works and lists chat records in listTile. Everything is working well.

When user adds a new chat message then I post the that text message to server by API to store into database. It works and response status is 200 which means message has been added on server's database.

I have instance of newly added chat message, I want to append / add it to previously fetched Future<dynamic> result.

Kindly suggest me how can I do this? Can we update Future<dynamic> typed data? Thanks.

Upvotes: 0

Views: 269

Answers (1)

eeqk
eeqk

Reputation: 3862

Future can emit only one item by design. If you want to emit multiple items, use Stream: https://api.flutter.dev/flutter/dart-async/Stream-class.html

To get to know how to generate streams have a look on this: https://dart.dev/articles/libraries/creating-streams

Most likely what you want to do is use rxdart's BehaviorSubject or dart's StreamController (they share api, so just substitute the name, except for ValueStream, which is specific to rxdart, this one will have to be replaced with just Stream):

class Api {
  final _subject = BehaviorSubject<DataToDisplay>();
  ValueStream<DataToDisplay> get data => _subject.stream;


  void fetchData() {
    final data = downloadDataFromSomewhere();
    _subject.add(data);
  }
}

Then just create a StreamBuilder similarly to FutureBuilder.

Upvotes: 1

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