# Enums

## Automatically created enums

Enums are implemented automatically for any `atom` attribute with a `one_of` constraint. For example:

```elixir
# On the resource of type `:ticket`
attribute :type, :atom, one_of: [:foo, :bar, :baz]
```

This would produce an enum called `:ticket_type`/`TicketType`.

## Custom enums

You can implement a custom enum by first adding the enum type to your absinthe schema (more [here](https://hexdocs.pm/absinthe/Absinthe.Type.Enum.html)). Then you can define a custom Ash type that refers to that absinthe enum type.

```elixir
# In your absinthe schema:

enum :status do
  value(:open, description: "The post is open")
  value(:closed, description: "The post is closed")
end
```

```elixir
# Your cusotm Ash Type
defmodule AshGraphql.Test.Status do
  use Ash.Type

  @values [:open, :closed]
  @string_values Enum.map(@values, &to_string/1)

  def graphql_input_type(_), do: :status
  def graphql_type(_), do: :status

  @impl true
  def storage_type, do: :string

  @impl true
  def cast_input(value, _) when value in @values do
    {:ok, value}
  end

  def cast_input(value, _) when is_binary(value) do
    value = String.downcase(value)

    if value in @string_values do
      {:ok, String.to_existing_atom(value)}
    else
      :error
    end
  end

  @impl true
  def cast_stored(value, _) when value in @values do
    {:ok, value}
  end

  def cast_stored(value, _) when value in @string_values do
    {:ok, String.to_existing_atom(value)}
  rescue
    ArgumentError ->
      :error
  end

  @impl true
  def dump_to_native(value, _) when is_atom(value) do
    {:ok, to_string(value)}
  end

  def dump_to_native(_, _), do: :error
end
```