get asynchronous value from firebase firestore reference

Question

I'm trying to get the name value from this promise from firebase firestore database:

(as for information I have a places colection that have a place containing a name and a ownerReference that references an owner document containing a name only.)

var names: any = [];
this.props.places.snapshot.docs.forEach((doc : any) => {
  const place = doc.data()
  place.ownerReference.get().then((snap : any) => {
    name.push(snap.data().name);
    console.log(names);
  })
});
console.log(names);

the first console log return the desired data, the last one returns an empty object, I know this is happening because of the asynchronous nature of a promise , but how can I get the desired value assigned to this variable?

score 2 · Accepted Answer · answered Jun 27 '18 at 19:20

2

Collect all the promises from each get() into an array, then use Promise.all() to wait until they are all done. Iterate the resulting snapshots in the callback after that.

const promises = []
this.props.places.snapshot.docs.forEach((doc : any) => {
    const place = doc.data()
    promises.push(place.ownerReference.get())
})

Promise.all(promises).then(snapshots => {
    const names = []
    snapshots.forEach(snapshot => {
        names.push(snapshot.data().name)
    })
    console.log(names);  // this prints what you want
})

answered Jun 27 '18 at 19:20

Doug Stevenson

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Way easier with Array.map – Jonas Wilms Jun 27 '18 at 19:24
1

@JonasW. Sure, but the OP didn't use it, so I didn't want to conflate the issue. – Doug Stevenson Jun 27 '18 at 19:43
got this erro: Property 'data' does not exist on type '{}' o this line `names.push(snapshot.data().name)` – Gustavo Freire Jun 27 '18 at 19:44
1

Nevermind, is was a typescript issue (did not specify the types on snapshots), sothis answer is no doubt correct, thanks a lot – Gustavo Freire Jun 27 '18 at 19:52
@GustavoFreire Yep exactly typescript d.ts nice catch – Matej Maloča Apr 19 '19 at 09:50

get asynchronous value from firebase firestore reference

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