创建流观看列表?

Question

我有一个这样的全局列表:

var data = [1,2,3];

我将向它添加更多的元素，每次这样做时，我都希望通知其他东西—我需要一个流和侦听器。所以我可以制造一条小溪，让它往下沉。在列表发生变化时添加?

var stream = Stream.fromIterable(data);
stream.listen((item) => print(item));
> 1
> 2
> 3
data.add(4);
> Uncaught Error: Concurrent modification during iteration
data.remove(3);
> Uncaught Error: Concurrent modification during iteration

哦,不。我该怎么做才能让它发挥作用呢?

Answer 1

这可能有帮助:

import 'dart:async';
class  ObservableList<T> {
final _list = <T>[];

final _itemAddedStreamController = StreamController<T>();

final _listStreamController = StreamController<List<T>>();

Stream get itemAddedStream => _itemAddedStreamController.stream;

Stream get listStream => _listStreamController.stream;


void add(T value) {
_list.add(value);
_itemAddedStreamController.add(value);
_listStreamController.add(_list);
}

void dispose() {
_listStreamController.close();
_itemAddedStreamController.close();
}
}
void main() {
final observableList = ObservableList<int>();

observableList.itemAddedStream.listen((value) => print(value));

observableList.add(1);
observableList.add(2);
observableList.add(3);
observableList.add(4);
}