Monitoring changes in the Firebase database using TypeScript

Question

Monitoring changes in the Firebase database using TypeScript

Currently, I am accessing my firebase realtime database through an angular service with the following code:

readItems() {
    return this.af.database.ref(`/path`)
      .on('value', snap => this.callback(snap.val()));
  }

The callback function is used to modify the response as needed. My challenge now is to retrieve this modified data in the component where I make the call to readItems. Here's how I'm making that call in the component:

this.service.readItems();

I am looking for a way to detect when this process completes and get the modified response using an observable or promise along with either subscribe or then. Unfortunately, I am struggling to implement this and would greatly appreciate any assistance.

angular typescript firebase firebase-realtime-database angular5

Answer 1

Answer №1

If you want to incorporate a Subject from rxjs into the callback function that you provide to the on method and then subscribe to it, here's how you can do it:

valueUpdated$ = new Subject();

callback(updatedValue) {
    // perform some operations ...
    valueUpdated$.next(updatedValue); // pass any necessary data to be received in the subscription
}

fetchData() {
  return this.af.database.ref(`/path`)
    .on('value', snapshot => this.callback(snapshot.val()));
}

Later on in your code, you can subscribe to the Subject like this:

this.valueUpdated$.subscribe(data => handleData(data));
this.service.fetchData();

Answer 2

If you want to incorporate a Subject from rxjs into the callback function that you provide to the on method and then subscribe to it, here's how you can do it:

valueUpdated$ = new Subject();

callback(updatedValue) {
    // perform some operations ...
    valueUpdated$.next(updatedValue); // pass any necessary data to be received in the subscription
}

fetchData() {
  return this.af.database.ref(`/path`)
    .on('value', snapshot => this.callback(snapshot.val()));
}

Later on in your code, you can subscribe to the Subject like this:

this.valueUpdated$.subscribe(data => handleData(data));
this.service.fetchData();

Monitoring changes in the Firebase database using TypeScript

Answer №1

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