Is there a way for me to implement a service method that retrieves the onSnapshot result, allowing me to seamlessly integrate it into my Component or Ionic Page?

Question

Is there a way for me to implement a service method that retrieves the onSnapshot result, allowing me to seamlessly integrate it into my Component or Ionic Page?

Currently, I am using "ionic-angular": "3.7.1" along with Firebase Cloud Firestore. My goal is to retrieve all the documents from the Post collection whenever they are updated, deleted, or added. I have been informed that by calling the onSnapshot Method, I can achieve this. Therefore, I have defined this method in a service.

getPosts(token: string){
  const userId = this.authService.getActiveUser().uid;
  let posts = [];
  return firebase.firestore().collection("Post").onSnapshot(function(querySnapshot) {
      querySnapshot.forEach(function(doc) {
          posts.push(doc.data());
        });
        console.log("Posts: ", posts.join(", "));
        return posts;
      });
}

Although I am able to see all my posts within the array 'Posts' in the console, when I call this method using this.post.getPosts(token) in my component, I receive the following output in the console:

ƒ () {
  asyncObserver.mute();
  firestoreClient.unlisten(internalListener);
}

Therefore, I am seeking guidance on how to create a method in a service that can provide the result of onSnapshot and allow me to utilize it in my Component or Ionic Page effectively.

Helpful Documentation:

https://firebase.google.com/docs/reference/js/firebase.firestore.Query?hl=es-419

https://firebase.google.com/docs/firestore/query-data/listen?hl=es-419

angular typescript firebase ionic3 google-cloud-firestore

Answer 1

Answer №1

Latest Update:

For those seeking guidance on how to incorporate a generic service/provider with Firestore, please refer to this informative article.

Past Feedback:

Utilizing fat arrow functions is recommended in this scenario, and there are a few errors that need to be addressed. You can test the following code:

  getPosts(token: string){
    const userId = this.authService.getActiveUser().uid;
    let posts = [];

     return firebase.firestore().collection("Post").get().then((querySnapshot)=> 
     {
       querySnapshot.forEach((doc)=> {
           posts.push(doc.data());
      });
        return posts;
     });
 }

Documentation Reference

Answer 2

Latest Update:

For those seeking guidance on how to incorporate a generic service/provider with Firestore, please refer to this informative article.

Past Feedback:

Utilizing fat arrow functions is recommended in this scenario, and there are a few errors that need to be addressed. You can test the following code:

  getPosts(token: string){
    const userId = this.authService.getActiveUser().uid;
    let posts = [];

     return firebase.firestore().collection("Post").get().then((querySnapshot)=> 
     {
       querySnapshot.forEach((doc)=> {
           posts.push(doc.data());
      });
        return posts;
     });
 }

Documentation Reference

Answer 3

Answer №2

Here is a suggested implementation:

To retrieve data, create an Observable in your service:

getPosts(token: string) {
  const userId = this.authService.getActiveUser().uid;
  let posts = [];
  return new Observable(observer => {
    const unsubscribe = firebase.firestore().collection("Post").onSnapshot(querySnapshot => {
      querySnapshot.forEach(function(doc) {
        posts.push(doc.data());
      });

        observer.next(posts);
      });

    return () => {
      unsubscribe();
    };
  });
}

In your Component or Ionic Page:

const _this = this; // 'this' inside 'subscribe' refers to the observable object
this.postsObserver = this.branchService.getPosts(token);
this.postsObserver
  .subscribe({
    next(posts) {
      _this.posts = posts;
    },
    error(error) { console.log(error); }, // optional
  });

Any changes made to your posts will automatically update the list without needing to call getPosts again.

Note:

If your service solely deals with posts, it's recommended to maintain a single reference to the posts collection when initializing the service:

  this.postsRef = firebase.firestore().collection('Post');

Although

firebase.firestore().collection('Post')

doesn't affect your database quota, using this.postsRef keeps the code cleaner for subsequent queries.

Edit:

An added "teardown" function is included to stop the Firebase realtime listener and free up client bandwidth when the Observable is destroyed.

References:

Answer 4

Here is a suggested implementation:

To retrieve data, create an Observable in your service:

getPosts(token: string) {
  const userId = this.authService.getActiveUser().uid;
  let posts = [];
  return new Observable(observer => {
    const unsubscribe = firebase.firestore().collection("Post").onSnapshot(querySnapshot => {
      querySnapshot.forEach(function(doc) {
        posts.push(doc.data());
      });

        observer.next(posts);
      });

    return () => {
      unsubscribe();
    };
  });
}

In your Component or Ionic Page:

const _this = this; // 'this' inside 'subscribe' refers to the observable object
this.postsObserver = this.branchService.getPosts(token);
this.postsObserver
  .subscribe({
    next(posts) {
      _this.posts = posts;
    },
    error(error) { console.log(error); }, // optional
  });

Any changes made to your posts will automatically update the list without needing to call getPosts again.

Note:

If your service solely deals with posts, it's recommended to maintain a single reference to the posts collection when initializing the service:

  this.postsRef = firebase.firestore().collection('Post');

Although

firebase.firestore().collection('Post')

doesn't affect your database quota, using this.postsRef keeps the code cleaner for subsequent queries.

Edit:

An added "teardown" function is included to stop the Firebase realtime listener and free up client bandwidth when the Observable is destroyed.

References:

Is there a way for me to implement a service method that retrieves the onSnapshot result, allowing me to seamlessly integrate it into my Component or Ionic Page?

Answer №1

Answer №2

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