How to update data in an array of objects in Firestore using Kotlin?

Question

How can I modify in the single item the value of a single field, for example, the id, and leave all the other fields at the initial value without having to delete and reinsert the item?

Answer 1

If you want to modify individual objects of an array type field, you have to read the document, modify the array on the client, then update the modified array back to the document in Firestore.

Please note, that you cannot do that without reading the document first. Assuming that you have a data class that looks like this:

data class Place(
    var id: String? = null,
    var isCancelled: Boolean? = null,
    var price: String? = null,
    var reservationName: String? = null,
    var reservationPhone: String? = null,
)

For reading the array of objects, the simplest method I can think of is to get the array as a list of "Place" objects ( List<Place> ) and right after that update the desired element according to your needs.

Answer 2

It may be late to answer but here is the solution

val washingtonRef = db.collection("cities").document("DC")

// Atomically add a new region to the "regions" array field.
washingtonRef.update("regions", FieldValue.arrayUnion("greater_virginia"))

// Atomically remove a region from the "regions" array field.
washingtonRef.update("regions", FieldValue.arrayRemove("east_coast"))

Here is the link you can also read

https://firebase.google.com/docs/firestore/manage-data/add-data#update_fields_in_nested_objects