node.js - 如何用观察者替换订阅者？

Question

This GitHub 上的问题几乎概括了这一点。我使用 timer() 和 1 秒的循环计划来执行特定任务。我将其与订阅者配对以订阅间隔。当某个模型的数据耗尽时，我会取消订阅它并等待新的到来。当他们的数据再次填充时，我尝试再次订阅，但它不起作用。事实证明，当订阅者被取消订阅时，我无法再次使用它。所以我必须用观察者来替换它。我是新手，不知道该怎么做。尝试查看示例，它们只是让我更加困惑。

如何替换以下代码以使用 Observer 来运行？

private timer = timer(1000, 1000);

// A timer subscription that keeps sending new images to the observer
timerSubscription = new Subscriber(() => {

    // Check if there is an element in the list
    if (this.head != null) {

      // If the current node at head is a folder, unsubscribe the listener
      if (this.head.data['id'].startsWith('folder')) {
        this.timerSubscription.unsubscribe();
      }

      // Pop a node from the list and pass on to observer
      this.observer.next(this.this$PiFrame.pop());

    } else {

      // If no nodes are left, unsubscribe from the timer
      this.timerSubscription.unsubscribe();

      console.log('No items left on the queue. Deactivating timer subscription.');
    }
  }, e => {}, () => {});

我像这样订阅:

    ...
    // Setup a timer to pop every 1000 ms
    this.timer.subscribe(this.this$PiFrame.timerSubscription);
    ...
    // If no nodes are left, unsubscribe from the timer
    this.timerSubscription.unsubscribe();
    ...

Answer 1

不要按照您的方式创建订阅，而是让 Observable 返回订阅。

将逻辑保留在函数中，如下所示:

  doWhatever() {
    console.log("tick")

    // Check if there is an element in the list
    if (this.head != null) {

      // If the current node at head is a folder, unsubscribe the listener
      if (this.head.data['id'].startsWith('folder')) {
        this.timerSubscription.unsubscribe();
      }

      // Pop a node from the list and pass on to observer
      this.observer.next(this.this$PiFrame.pop());

    } else {

      // If no nodes are left, unsubscribe from the timer
      this.timerSubscription.unsubscribe();

      console.log('No items left on the queue. Deactivating timer subscription.');
    }
  }

然后，当您想要订阅时:

this.timerSubscription = this.timer.subscribe(() => this.doWhatever());

这可以重复使用，因为每个订阅都会生成一个新的订阅