How To Save Belongs To - Ash 3.0 Error ""Ash.Resource.Change.ManageRelationship does not implement `atomic/3`"

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1

How to do I save belongs_to relationship?

I have Item and UnitMeasure resource. Item resource belongs to the UnitMeasure Resource.

Here is the relationship definition for the Item resource:

 relationships do belongs_to :unit_measure, Kamaro.Stock.UnitMeasure do attribute_writable? true end end

According to Ash Relationship Tutorial, the following code should work

item |> Ash.Changeset.for_update(:update, %{unit_measure_id: unit.id}) |> Ash.update()

But it is giving me an error that:

{:error, %Ash.Error.framework{ errors: [ %Ash.Error.Framework.MustBeAtomic{ resource: Kamaro.Stock.Item, action: :update, reason: "Ash.Resource.Change.ManageRelationship does not implement `atomic/3`", splode: Ash.Error, bread_crumbs: [], vars: [], path: [], stacktrace: #Splode.Stacktrace<>, class: :framework } ] }}
2

That tutorial may be a little out of date as it references Ash 2. It should work as-is though - have you customized the update action in any way, and added a manage_relationship call? If so, you can safely remove it as it’s not necessary.

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3

It worked after:

  1. I removed manage_relationship
  2. I added :unit_measure_id in the default_accept
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