FieldValue.increment not working on nested object

[pjc0247]

I have a object for balances(inventory) which contains various type of items.
however increment does not work well with this.

Here's an example

// This works
await this.ref.update({'gold': FieldValue.increment(1)});

// This does not work
await this.ref.update({
  balances: {
    [key]: FieldValue.increment(value)
  }
});

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[var-const]

If you'd like to update an existing nested field, you need to specify a dot-separated path to the field as a key in the dictionary you supply to update. So in this case, it would look like this:

await this.ref.update({
  'balances.${key}': FieldValue.increment(value)
});

This snippet should work as expected.

(edit: alternatively, you could use set with merge: true if you'd prefer to keep the syntax more similar to your original code:

await this.ref.set({
  balances: {
    [key]: FieldValue.increment(value)
  }
}, { merge: true });

)

The behavior of the code snippet you posted is different -- it overwrites the field balances with a completely new dictionary. When FieldValue.increment is applied to a not-yet-existing field, it behaves as if the field has a zero value, effectively setting the field to the value of increment.

Please let me know if the code snippet I posted works for you. I will close the issue for now, but feel free to follow up on this thread if you're still having any trouble while using a dot-separated path.