AE
Ash Elixir•2y ago
Chris

read action returning a boolean

Hi, I'm trying to make a resource to represent some global boolean flags for some features in my application. I'm just having trouble figuring out how to writing an action to return a boolean. 
defmodule Foo.Bar.LiveFeatureFlags do
  use Ash.Resource, data_layer: AshPostgres.DataLayer

  postgres do
    table "live_feature_flags"
    repo Repo
  end

  atributes do
    uuid_primary_key :id

    attribute :name, :string, allow_nil?: false
    attribute :description, :string, allow_nil?: false
    attribute :is_enabed, :boolean, allow_nil?: false
  end

  actions do
    defaults [:create, :read, :update, :destroy]

    read :is_enabled? do
      argument :name, :string do
        allow_nil? false
      end

      filter expr(name == ^arg(:name))
      get? true
    end
  end

  code_interface do
    define :create
    define :read
    define :update
    define :destroy
  end
end
defmodule Foo.Bar.LiveFeatureFlags do
  use Ash.Resource, data_layer: AshPostgres.DataLayer

  postgres do
    table "live_feature_flags"
    repo Repo
  end

  atributes do
    uuid_primary_key :id

    attribute :name, :string, allow_nil?: false
    attribute :description, :string, allow_nil?: false
    attribute :is_enabed, :boolean, allow_nil?: false
  end

  actions do
    defaults [:create, :read, :update, :destroy]

    read :is_enabled? do
      argument :name, :string do
        allow_nil? false
      end

      filter expr(name == ^arg(:name))
      get? true
    end
  end

  code_interface do
    define :create
    define :read
    define :update
    define :destroy
  end
end
The behaviour I'd like for is_enabled? is for it to return true if the feature of the specified name doesn't exist or return true if the feature of the specified name does exist and is_enabled is true, otherwise return false. How can I make an action return a boolean and how can I get it to have that custom logic? Cheers, Chris.
2 Replies
jart
jart•2y ago
Hey Chris. You probably want split it into two actions - one read which gets the data you need and a generic action which can return an arbitrary type which calls the read action and returns the required Boolean.
Chris
ChrisOP•2y ago
thanks, having a go now 
defmodule Blah.Blah.LiveFeatureFlags do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets
  require Ash.Query

  actions do
    defaults([:create, :read, :destroy])
  end

  attributes do
    uuid_primary_key(:id)
    attribute(:name, :string, allow_nil?: false)
    attribute(:is_enabled, :boolean, allow_nil?: false)
  end

  code_interface do
    define_for(Blah.Blah)
    define(:create)
    define(:read)
    define(:destroy)
  end

  def is_enabled?(name) do
    __MODULE__
    |> Ash.Query.for_read(:read)
    |> Ash.Query.filter(name == ^name)
    |> Blah.Blah.read!()
    |> case do
      [%{is_enabled: is_enabled} | _] -> is_enabled
      _ -> true
    end
  end
end
defmodule Blah.Blah.LiveFeatureFlags do
  use Ash.Resource, data_layer: Ash.DataLayer.Ets
  require Ash.Query

  actions do
    defaults([:create, :read, :destroy])
  end

  attributes do
    uuid_primary_key(:id)
    attribute(:name, :string, allow_nil?: false)
    attribute(:is_enabled, :boolean, allow_nil?: false)
  end

  code_interface do
    define_for(Blah.Blah)
    define(:create)
    define(:read)
    define(:destroy)
  end

  def is_enabled?(name) do
    __MODULE__
    |> Ash.Query.for_read(:read)
    |> Ash.Query.filter(name == ^name)
    |> Blah.Blah.read!()
    |> case do
      [%{is_enabled: is_enabled} | _] -> is_enabled
      _ -> true
    end
  end
end
I wasn't able to figure out how to use a generic action but this does the job

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