Stream Listening For List Updates - flutter

Question

I'm trying to understand how to use streams to notify listeners when there is a new addition to a list, below I wrote an example program that sums up what I'm trying to accomplish. Everytime there is a NEW string added to the existing 'names' list, I would like the stream to notify its listeners.
import 'dart:async';
import 'dart:io';
import 'dart:math';
List<String> names = ['matt', 'luke', 'sam'];
// pushes random string onto 'names' list every 3 seconds
void addNamesToNameList() async {
Random random = Random();
int len = 4;
while(true) {
String new_name = String.fromCharCodes(List.generate(len, (index) => random.nextInt(33) + 89));
names.add(new_name);
print("Added $new_name to names list");
sleep(Duration(seconds: 3));
}
}
void main() {
addNamesToNameList();
/*
Insert stream that is notified every time there is a NEW addition to the 'names' list
*/
}

Answer 1

You can use Stream.periodic to accomplish this.
late final List<String> names = [];
late final Stream<String> stream = randomStream().asBroadcastStream();
//use [asBroadcastStream] if you have multiple listeners.
String generateNewName(int i) {
Random random = Random();
int len = 4;
return String.fromCharCodes(
List.generate(len, (index) => random.nextInt(33) + 89));
}
Stream<String> randomStream() async* {
yield* Stream.periodic(
const Duration(seconds: 3),
generateNewName,
).asyncMap((event) => event);
}
and then listen to changes:
stream.listen((event) {
setState(() => names.add(event));
});