Ash Framework•2mo ago

Changing attributes in action

I am trying to simplify the commented out code by using expr() , but i get an InvalidAttributeError with the hint string_downcase(nil)

    create :create do
      accept [:name]
      
      # what i want, but does not work
      change set_attribute(:name, expr(string_downcase(^arg(:name))))
      
      # what works
      change fn changeset, _ ->
        new_name =
          Ash.Changeset.get_argument_or_attribute(changeset, :name)
          |> String.downcase()

        Ash.Changeset.update_change(changeset, :name, new_name)
      end
    end

    create :create do
      accept [:name]
      
      # what i want, but does not work
      change set_attribute(:name, expr(string_downcase(^arg(:name))))
      
      # what works
      change fn changeset, _ ->
        new_name =
          Ash.Changeset.get_argument_or_attribute(changeset, :name)
          |> String.downcase()

        Ash.Changeset.update_change(changeset, :name, new_name)
      end
    end

Also I am not sure if to put it in before_action or not since from what I saw the change does not appear in the Phoenix form. So in both cases it should only appear in the database ?

Solution:

You can't use expressions in that context

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5 Replies

Abu kumathra•2mo ago

you don't have any arguments in the action just like the error states maybe replace ^arg(:name) with name

RiseOP•2mo ago

iex(6)> Tunez.Music.create_artist(%{name: "Test"})
{:error,
 %Ash.Error.Invalid{
   bread_crumbs: ["Error returned from: Tunez.Music.Artist.create"],
   changeset: "#Changeset<>",
   errors: [
     %Ash.Error.Changes.InvalidAttribute{
       field: :name,
       message: "is invalid",
       private_vars: nil,
       value: string_downcase(name),
       has_value?: true,
       splode: Ash.Error,
       bread_crumbs: ["Error returned from: Tunez.Music.Artist.create"],
       vars: [],
       path: [],
       stacktrace: #Splode.Stacktrace<>,
       class: :invalid
     }
   ]
 }}

iex(6)> Tunez.Music.create_artist(%{name: "Test"})
{:error,
 %Ash.Error.Invalid{
   bread_crumbs: ["Error returned from: Tunez.Music.Artist.create"],
   changeset: "#Changeset<>",
   errors: [
     %Ash.Error.Changes.InvalidAttribute{
       field: :name,
       message: "is invalid",
       private_vars: nil,
       value: string_downcase(name),
       has_value?: true,
       splode: Ash.Error,
       bread_crumbs: ["Error returned from: Tunez.Music.Artist.create"],
       vars: [],
       path: [],
       stacktrace: #Splode.Stacktrace<>,
       class: :invalid
     }
   ]
 }}

Unfortunatly not even when it is passed as an argument it fails with value: string_downcase("Test") :/

Solution

ZachDaniel•2mo ago

You can't use expressions in that context

ZachDaniel•2mo ago

You can do atomic_update but that only works for update actions I'd start with atomic_update and do a custom change if that wasn't sufficient

RiseOP•2mo ago

okay, since I want to have it in the create action the custom change wil be the way to go. Thanks 🙂

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Changing attributes in action

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