Cannot update an array in Firestore due an error

Question

I have this data class in Kotlin:

data class Product(
    var id: String? = null,
    var name: String? = null,
    @ServerTimestamp
    var createdAt: Date? = null
): Serializable

And this Firestore database:

Root
 \
 carts <- collection
   \
   cartId <- document
     \
     products: [productObj, productObj, productObj]

And I'm trying to add another Product object to the list. I'm using this line:

cartsRef.document(cartId).update("products", FieldValue.arrayUnion(product)).addOnCompleteListener {}

And I get the following error:

java.lang.IllegalArgumentException: Invalid data. FieldValue.serverTimestamp() can only be used with set() and update()

Why do I get this error since I am using update() function?

@Walid Just tried to change the `product` object to a Map, and I get the same error. Any ideas? — Ivan Patrice, Jul 09 '20 at 12:40
It might simply be the case that `@ServerTimestamp` does not work with objects passed to `FieldValue.arrayUnion()`. — Doug Stevenson, Jul 09 '20 at 16:46

score 0 · Answer 1 · answered Jul 10 '20 at 01:15

0

In your Data class you should try changing the @ServerTimestamp to

@ServerTimestamp private val serverTimestamp:Date

answered Jul 10 '20 at 01:15

maniSidhu98

What else have you tried? There's also [this](https://stackoverflow.com/questions/57534290) that may also be of help. – maniSidhu98 Jul 17 '20 at 02:26

score 0 · Answer 2 · answered May 31 '22 at 15:09

0

@ServerTimestamp private val yourDate: Date? = null

Key points are that it has to be private and nullable with default value null, or if not default, set null in constructor

answered May 31 '22 at 15:09

Antonis Radz

2 Answers2