Firestore: How to update specific field of document?

问题

How do I access and update a specific field in angular firestore:

回答1:

Ok you have to do the following steps:

First make sure that you create a query either on name or ID or even both, it need to be unique
Then you subscribe to this query with snapshotChanges
Next you will get the id from the queried objects
After this you use this id to update the doc with the new value

It would look something like this:

updateDoc(_id: string, _value: string) {
  let doc = this.afs.collection('options', ref => ref.where('id', '==', _id));
  doc.snapshotChanges().pipe(
    map(actions => actions.map(a => {                                                      
      const data = a.payload.doc.data();
      const id = a.payload.doc.id;
      return { id, ...data };
    }))).subscribe((_doc: any) => {
     let id = _doc[0].payload.doc.id; //first result of query [0]
     this.afs.doc(`options/${id}`).update({rating: _value});
    })
}

回答2:

It should be pretty easy task. You can use update function and pass the field name and value to update.

ex :

this.db.doc(`options/${id}`).update({rating:$rating}); //<-- $rating is dynamic

回答3:

Is very simple (.collection) to declare the collection that u want to change (.doc) to specify the id of the document that u want to update and the in (.update) just put the update field that u want change it

 constructor(private db: AngularFirestore) {}
 this.db
  .collection('options')
  .doc('/' + 'mzx....')
  .update({rating: value})
  .then(() => {
    console.log('done');
  })
  .catch(function(error) {
   console.error('Error writing document: ', error);
  });

回答4:

If your id is unique, only return one query result, I found there is no need to pipe - map.

updateDoc(_id: string, _value: string) {
  let doc = this.afs.collection('options', ref => ref.where('id', '==', _id));
  doc.snapshotChanges().subscribe((res: any) => {
    let id = res[0].payload.doc.id;
    this.afs.collection('options').doc(id).update({rating: _value});
  });
}

来源：https://stackoverflow.com/questions/53184131/firestore-how-to-update-specific-field-of-document

标签

angular

firebase

google-cloud-firestore