Delete a field from Firestore, with a dynamic key

Question

I am trying to delete a single field from a Document in Firestore The Key of the field is held in a variable e.g.

var userId = "random-id-1"

In the document I have a field of members structured like this:

{
  members:{
    random-id-1:true,
    random-id-2:true
  }
}

I would like to delete random-id-1:true, but keep random-id-2:true

How is this possible without getting the entire members object and writing an updated object?

I have tried this, however I get the error: Document references must have an even number of segments

and I also tried this:

db.collection('groups').doc(this.props.groupId).set({
  members: {
    [userId]: firebase.firestore.FieldValue.delete()
  }
},{merge: true})

However I get the error: Function DocumentReference.update() called with invalid data. FieldValue.delete() can only appear at the top level of your update data

Thanks for any help

Answer 1

I have managed to delete a field like this:

let userId = "this-is-my-user-id"
let groupId = "this-is-my-group-id"

db.collection('groups').doc(groupId).update({
  ['members.' + userId]: firebase.firestore.FieldValue.delete()
})

This is using the dot operator method described here

Please let me know if there are any alternative methods to this

Thanks

Answer 2

I had to import FieldValue

https://firebase.google.com/docs/firestore/manage-data/delete-data#fields

        // Get the `FieldValue` object
        var FieldValue = require('firebase-admin').firestore.FieldValue;
        
        // Create a document reference
        var cityRef = db.collection('cities').doc('BJ');
        
        // Remove the 'capital' field from the document
        var removeCapital = cityRef.update({
          capital: FieldValue.delete()
        });