如何用观察者替换订阅者？

Question

This GitHub 上的问题非常概括。我正在使用 timer() 以 1 秒的重复计划执行某项任务。我将它与Subscriber 配对以订阅间隔。当某个模型的数据用完时，我会取消订阅它并等待新的到来。当他们再次填充数据时，我尝试再次订阅，但它不起作用。事实证明，当Subscriber 被取消订阅时，我无法再次使用它。所以我必须用Observer 替换它。这里是新手，我不知道该怎么做。试着看例子，他们让我更加困惑。

如何将以下代码替换为Observer？

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 => {}, () => {});

我是这样订阅的：

    ...
    // 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

不要以您的方式创建订阅，而是让Observable 返回订阅。

将逻辑保存在函数中，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.');
    }
  }

那么，当你想订阅时：

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

这可以重复使用，因为每个subscribe 都会生成一个新的Subscription