Mapping Firestore documents to an array using AngularFire - A step-by-step guide to using valueChanges

In my Angular web application, I'm utilizing the AngularFire library to interact with Firestore database.

Within the constructor of a component, I want to subscribe to a collection of documents and map these documents to an array whenever the value changes function is triggered.

Rendering this list in the frontend is easily achievable using the provided syntax.

// Component Constructor
constructor(private afs: AngularFirestore) {
    this.itemsCollection = afs.collection<Item>('items');
    this.items = this.itemsCollection.valueChanges();
}


// Component Template
<ul>
  <li *ngFor="let item of items | async">
    {{ item.name }}
  </li>
</ul>

However, I require an array (or object) of the documents within that collection for additional logic in rendering other elements. For instance, I have an "isChecked" function that determines if a checkbox should be checked based on whether an item exists in the document collection.

async isChecked(itemID) {
    if(items[itemID]) {
     return true;
     } else {
     return false;
     }
}

So, the question remains - how can I retrieve the documents into another variable while ensuring it stays updated with valueChanges?

Answer №1

this.fetchItems()
.pipe(
  tap(response => {
   this.items = response;
  })
)
.subscribe();

Following this, you should eliminate the async pipe from the HTML. By doing so, you can access items directly as an object or array instead of an observable, which may simplify things for you. Remember to also unsubscribe in ngOnDestroy.

Answer №2

To implement this functionality, consider utilizing the rxjs map method.

this.collection = this.dataCollection.values().stream().map(result => ...);

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