Firestore get values into array, instead it comes as undefined

Question

I currently working on a mobile application using the front-end framework Ionic and angularjs with typescript and for the backend I'm using firebase. My problem is that when I make a call to my firebase nosql database I can't get it my items into an typescript array in order to get the data to the screen because when I call the variable containing the values it comes as undefined. Here is my code:

getSingleDatabase(){
this.collectionReference=this.db.collection('posts');
      this.collectionReference.get()
  .then(snapshot =>{
  snapshot.forEach(doc => {

    this.firstGet.push(doc.data());
  });
})
.catch(err =>{
  console.log(err);
});
return this.firstGet;

}

Doug Stevenson · Accepted Answer · 2018-03-09 16:58:19Z

1

Firstore APIs are asynchronous, meaning your call to get() returns immediately with a promise that indicates when the fetch is actually complete. It could take any amount of time until the promise is fulfilled with the document you're looking for. As a result, your getSingleDatabase function is going to return before the data is available in this.firstGet. You will be able to see what I mean if you put logging statements at every stage in your code.

The only way to know when the data is fully available is to use the promise returned by get(), which means you should not be expecting this.firstGet to contain anything until the promise is fulfilled.

Please read more about why Firebase APIs are asynchronous and what to expect from them.

answered Mar 9, 2018 at 16:58

Doug Stevenson

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