Question

我如何构建一个只有＆＃34;继续前进的观察者？独立于任何订阅者（即refCount等等问题）并为后期订阅者提供最新的价值？

以下是我的尝试：

// Approach 1
const myObservable$ = Rx.Observable.timer(0, 1000).publish();
myObservable.connect();
myObservable$.subscribe(x => console.log(x));
setTimeOut(function () {
  myObservable$.subscribe(x => console.log("late", x));
}, 3500);

// 0
// 1
// 2
// 3
// 4
// late 4
// 4
// late 5
// ...

方法1的问题在于t = 3.5s的后期订户没有获得＆＃34;当前价值＆＃34; 3。我想要的是

的输出

// 0
// 1
// 2
// 3
// late 3
// 4
// late 4
// ...

另一种方法使用publishValue：

// Approach 2
const myObservable$ = Rx.Observable.timer(0, 1000).publishValue();
myObservable.connect();
myObservable$.subscribe(x => console.log(x));
setTimeOut(function () {
  myObservable$.subscribe(x => console.log("late", x));
}, 3500);

// undefined
// 0
// 1
// 2
// 3
// late 3
// 4
// late 4
// ...

在方法2中，已故用户获得正确的＆＃34; t = 3.5s时的值。这种方法的问题是我们需要提供一个初始我们可能并不总是拥有的价值。

// Approach 3
const myObservable$ = Rx.Observable.timer(0, 1000).replay(1);
myObservable.connect();
myObservable$.subscribe(x => console.log(x));
setTimeOut(function () {
  myObservable$.subscribe(x => console.log("late", x));
}, 3500);

// 0
// 1
// 2
// 3
// late 0
// late 1
// late 2
// late 3
// 4
// late 4
// ...

此时我迷路了。我的印象是.replay(1) 可能会解决我的问题但不知何故它会重播多个事件。

有什么想法吗？

Answer 1

方法3是您问题的正确答案。但是，您使用的是interface incorrectly。

  /**
   *
   * @example
   * var res = source.replay(null, 3);
   * var res = source.replay(null, 3, 500);
   * var res = source.replay(null, 3, 500, scheduler);
   * var res = source.replay(function (x) { return x.take(6).repeat(); }, 3, 500, scheduler);
   *
   * @param selector [Optional] Selector function which can use the multicasted source sequence as many times as needed, without causing multiple subscriptions to the source sequence. Subscribers to the given source will receive all the notifications of the source subject to the specified replay buffer trimming policy.
   * @param bufferSize [Optional] Maximum element count of the replay buffer.
   * @param windowSize [Optional] Maximum time length of the replay buffer.
   * @param scheduler [Optional] Scheduler where connected observers within the selector function will be invoked on.
   * @returns {Observable} An observable sequence that contains the elements of a sequence produced by multicasting the source sequence within a selector function.
   */
Rx.Observable.prototype.replay([selector], [bufferSize], [window], [scheduler])

您需要使用第一个重载source.replay(null, 3)，因此您的代码应为：

const myObservable$ = Rx.Observable.timer(0, 1000).replay(null, 1);
myObservable$.connect();
myObservable$.subscribe(x => console.log(x));
setTimeout(function () {
  myObservable$.subscribe(x => console.log("late", x));
}, 3500);

＆＃34;当前价值＆＃34;的概念独立于订阅者

1 个答案: