Query one-to-one relationship data in :create action

Ash Forum Ash Questions / Help
,
1

I have 3 resources. When creating reading I would like to pass tag_id and inside of :create function query employee to get employee.id and populate reading.employee_id with that value.

Tag:

  attributes do
    uuid_primary_key :id do
      description "Primary ID"
    end

    attribute :code, :string do
      allow_nil? false
      description "Id of the physical tag/card"
    end
  end

  identities do
    identity :unique_code, [:code]
  end

  relationships do
    belongs_to :employee, App.Api.Employee do
      description "Employee that is using this tag"
    end
  end

Employee:

  attributes do
    uuid_primary_key :id do
      description "Primary ID"
    end
  end

  relationships do
    has_one :tag, App.Api.Tag do
      description "Tag used for tracking"
    end

    has_many :readings, App.Api.Reading do
      description "User readings"
    end
  end

Reading:

  attributes do
    uuid_primary_key :id do
      description "Primary ID"
    end

  end

  relationships do
    belongs_to :employee, App.Api.Employee do
      attribute_writable? true
      description "Employee that created reading"
    end
  end

I’ve added managed_relationships to graphql block so I can send tag_id as argument to :create func but I have no idea what would be the best way to get employee.id based on tag_id?

graphql do
    type :reading

    managed_relationships do
      managed_relationship(:create_reading, :tag) do
        lookup_with_primary_key?(false)
        lookup_identities([:tag_id])
      end
    end
end
2

I’ve managed to do it. Now the question is: Is there a more optimal way?

  • Changed relationship between Tag and Employee to have employeeId field avaliable without having to load the relationship,
  • Added custom read fun to Tag resource:
      read :by_code do
    get? true
    argument :code, :string
    argument :tenant, :string

    get_by :code

    prepare fn query, _ ->
      Ash.Query.set_tenant(query, query.arguments[:tenant])
    end
  • Added create fun to Reading resource:
      create :test_create do
    argument :tag_id, :string

    change before_action(fn changeset ->
             {:ok, %{employee_id: employee_id}} =
               Timewise.Tracker.Tag.by_code(
                 Ash.Changeset.get_argument(changeset, :tag_id),
                 changeset.tenant
               )

             Ash.Changeset.change_attribute(changeset, :employee_id, employee_id)
           end)
  end

One thing left to do is add error handling to create function.

3

The way you`ve laid out is the simplest/potentially only realistic way to do it :+1:

4

Small notes about those steps:

  • First step is unclear as employee_id should have been available before, so no comment.

  • Second step has a lot of redundancy. 1) No need to specify get? true if get_by is used. 2) No need for argument :tenant as all actions have opts that include tenant. So the same action can be written as:

read :get_by_code do
  get_by :code
end
  • 3) But even that is not needed as I see that you use code interface to invoke the action. In that case you don’t actually need custom action at all and can use default read (that’s assumes that you have one) with get_by option like this:
code_interface do
  define :get_by_code, action: :read, get_by: :code
end
  • Third is step is okay one. To pass tenant with new step two you would do tenant: changeset.tenant as the second argument. 1) You have attribute_writable? true for employee_id but if you did it only for Changeset.change_attribute to work then you can remove the option and use Changeset.force_change_attribute. 2) In my opinion better to rename tag_id argument to tag_code for clarity. 3) Based on code it seems like the argument must be present, so good to add allow_nil?: false.
5

Oh, I hadn’t seen his reply when i said it was the simplest/only way :joy: I was responding to the first message.