Hi I’m trying to create a simple action to recommend and unrecommend.

For now logic that a person can only recommend one post at a time is implemented using identities.

thumb_up.ex

defmodule Dentallog.DentalLab.ThumbUp do
  use Ash.Resource,
    data_layer: AshPostgres.DataLayer,
    extensions: [
      AshGraphql.Resource
    ]

  graphql do
    type :dental_lab_post_thumb_up

    mutations do
      create :thumb_up_dental_lab_post, :thumb_up
      destroy :cancel_thumb_up_dental_lab_post, :cancel
    end
  end

  actions do
    defaults [:read]

    create :thumb_up do
      change relate_actor(:user)
    end

    destroy :cancel do
      change relate_actor(:user)
    end
  end

  attributes do
    uuid_primary_key :id

    create_timestamp :created_at
    update_timestamp :updated_at
  end

  relationships do
    belongs_to :user, Dentallog.Accounts.User do
      api Dentallog.Accounts
    end

    belongs_to :dental_lab_post, Dentallog.DentalLab.DentalLabPost do
      allow_nil? false
      attribute_writable? true
    end
  end

  postgres do
    table "dental_lab_thumb_ups"
    repo Dentallog.Repo
  end

  identities do
    identity :unique_thumbup, [:dental_lab_post_id, :user_id] do
      eager_check_with Dentallog.DentalLab
    end
  end
end

But I’m not sure what to do about the logic for canceling.
I guess I could use a changeset, but that’s a bit difficult.
Currently, the PK works this: if you enter an ID, it gets deleted.
But I’d like to get the input as the ID of the post and authenticate the user via relate_actor(:user). (post_id, user_id)

Is there a good way to do this?

Also, I’m wondering if you recommend using identities or atomic to allow for guarantee one-time recommendations.