How do I replace a subscriber with an Observer? - node.js

Question

This issue on GitHub pretty much sums it up. I'am using a timer() with a recurring schedule of 1 second to perform a certain task. I pair it up with a Subscriber to subscribe the intervals. When a certain model runs out of data, I unsubscribe it & wait for new arrivals. When they data is populated again, I try to subscribe again but it doesn't work. It turns out whena Subscriber has been unsub'd, I can't use it again. So I must replace it with an Observer. A newbie here, I've no idea how to do that. tried looking at examples, they just confused me further.
How do I replace the following code to function with an Observer instead?
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$PiFrame.pop());
} else {
// If no nodes are left, unsubscribe from the timer
this.timerSubscription.unsubscribe();
console.log('No items left on the queue. Deactivating timer subscription.');
}
}, e => {}, () => {});
and I subscribe like so :
...
// Setup a timer to pop every 1000 ms
this.timer.subscribe(this.this$PiFrame.timerSubscription);
...
// If no nodes are left, unsubscribe from the timer
this.timerSubscription.unsubscribe();
...

Answer 1

Instead of creating the subscription the way you do, let the Observable return the subscription.
Keep your logic in a function, like so:
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.');
}
}
Then, when you want to subscribe:
this.timerSubscription = this.timer.subscribe(() => this.doWhatever());
This can be used repeatedly, as each subscribe generates a new Subscription