Question

我正在使用combineLatest observable和两个流和选择器函数。

const todos = Rx.Observable.of([{
  id: 1,
  completed: false,
  text: 'one'
}, {
  id: 1,
  completed: true,
  text: 'two'
}]);

const filter = Rx.Observable.of('SHOW_ALL');


const getTodos = Rx.Observable.combineLatest(todos, filter, (todos, filter) => {
  console.log('calculation');
  // doing some calculation...
  return todos;
});

getTodos.subscribe(console.log)
getTodos.subscribe(console.log)

<script src="https://unpkg.com/@reactivex/rxjs@5.0.3/dist/global/Rx.js"></script>

我需要结果选择器只为订阅者运行一次以避免重新计算。例如，缓存结果，如果两个输入都没有变化，则给我最新的值。

有一种方法可以用RxJS做到这一点吗？

Answer 1

我认为您正在寻找shareReplay运营商。它允许您在所有订阅者之间共享combineLatest生成的值。 https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/sharereplay.md

如果您不想在订阅者从0到1或更多时自动连接/断开连接，您可能需要查看replay，反之亦然。 https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/replay.md

const getTodos = Rx.Observable.combineLatest(todos, filter, (todos, filter) => {
  console.log('calculation');
  // doing some calculation...
  return todos;
})
.shareReplay();

这是一个正在运行的例子：

＆＃13;

const todos = Rx.Observable.of([{
  id: 1,
  completed: false,
  text: 'one'
}, {
  id: 1,
  completed: true,
  text: 'two'
}]);

const filter = Rx.Observable.of('SHOW_ALL');

const getTodos = Rx.Observable.combineLatest(todos, filter, (todos, filter) => {
  console.log('calculation');
  // doing some calculation...
  return todos;
})
.shareReplay();

getTodos.subscribe(console.log.bind(console))
getTodos.subscribe(console.log.bind(console))

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/4.1.0/rx.lite.js"></script>

＆＃13;

RxJS只运行一次选择器功能

1 个答案: