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javascriptangularfirebase-realtime-databaseangularfire2

How to use valueChanges to only read data once in firebase database?

My ionic 5 (Angular) project uses Google firebase database.

This is an example code I used to read data from firebase database. I just want to read the data only once. As valueChanges() is a observable, I guess I have to unsubscribe the subscription every time when use it.

constructor(db: AngularFireDatabase) {
    this.tempsub = db.list('items').valueChanges().subscribe(data=>{...});
    this.tempsub.unsubscribe()
  }

Do I have to unsubscribe it in my use case? Is there a better solution to read the data from firebase database only once?

Solution

  • You can use the take operator to configure the desired number of emissions.
    Using take(1) will emit the first value, then complete and unsubscribe.

    db.list('items').valueChanges()
  .pipe(take(1))
  .subscribe(...);