AF
Ash Framework•2mo ago
aidalgol

Reducing some code duplication in Ash enums

I find myself defining a few enum modules in my application like this, 
defmodule MyApp.MyDomain.SomeEnum do
  use Ash.Type.Enum, values: [:foo, :bar, :blah]

  def label_for(category) do
    category
    |> Atom.to_string()
    |> String.capitalize()
  end

  @doc """
  Returns a list suitable for passing to `MyAppWeb.CoreComponents.input/1` when
  `type=select`.
  """
  def options_for_select do
    for category <- values() do
      {label_for(category), category}
    end
  end
end
defmodule MyApp.MyDomain.SomeEnum do
  use Ash.Type.Enum, values: [:foo, :bar, :blah]

  def label_for(category) do
    category
    |> Atom.to_string()
    |> String.capitalize()
  end

  @doc """
  Returns a list suitable for passing to `MyAppWeb.CoreComponents.input/1` when
  `type=select`.
  """
  def options_for_select do
    for category <- values() do
      {label_for(category), category}
    end
  end
end
Would it be appropriate to move these functions that I have copied across modules into a module and then use the module to bring them into my enum modules?
Solution:
I added some functions to Enum awhile back for this. Pretty sure there are some examples in the docs. https://hexdocs.pm/ash/Ash.Type.Enum.html#module-value-labels-and-descriptions...
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11 Replies
aidalgol
aidalgolOP•2mo ago
Something like this? 
defmodule MyApp.MyDomain.SomeEnum do
  use Ash.Type.Enum, values: [:foo, :bar, :blah]
  use MyApp.EnumWebHelpers
defmodule MyApp.MyDomain.SomeEnum do
  use Ash.Type.Enum, values: [:foo, :bar, :blah]
  use MyApp.EnumWebHelpers
defmodule MyApp.EnumWebHelpers do
  defmacro __using__(_opts) do
    quote do
      def label_for(category) do
        category
        |> Atom.to_string()
        |> String.capitalize()
      end

      @doc """
      Returns a list suitable for passing to `MyAppWeb.CoreComponents.input/1` when
      `type=select`.
      """
      def options_for_select do
        for category <- values() do
          {label_for(category), category}
        end
      end
    end
  end
end
defmodule MyApp.EnumWebHelpers do
  defmacro __using__(_opts) do
    quote do
      def label_for(category) do
        category
        |> Atom.to_string()
        |> String.capitalize()
      end

      @doc """
      Returns a list suitable for passing to `MyAppWeb.CoreComponents.input/1` when
      `type=select`.
      """
      def options_for_select do
        for category <- values() do
          {label_for(category), category}
        end
      end
    end
  end
end
The reason I don't just move the functions into another module and call them from there is that there are a couple special-case enums for which the implementations of these functions need to be different. And would this be a candidate for a behaviour?
sevenseacat
sevenseacat•2mo ago
I think the options_for_select functionality should be added to AshPhoenix - I'd generally err on the side of defining the labels for the enum values manually
aidalgol
aidalgolOP•2mo ago
When I did that for some of my longer enums, it felt very repetitive, and more error-prone than ndefining the labels manually only for the exceptions.
sevenseacat
sevenseacat•2mo ago
how does your code allow specifying labels for the exceptions?
aidalgol
aidalgolOP•2mo ago
If options_for_select were added to AshPhoenix, what would it call to determine the labels? Completely different implementation of these functions. e.g., in my enum for NZ regions, 
  def label_for(region) do
    case region do
      :bop ->
        "Bay of Plenty"

      :hawkes_bay ->
        "Hawke's Bay"

      :manawatu_wanganui ->
        "Manawatu-Wanganui"

      other ->
        other
        |> Atom.to_string()
        |> String.split("_")
        |> Enum.map_join(" ", &String.capitalize(&1))
    end
  end
  def label_for(region) do
    case region do
      :bop ->
        "Bay of Plenty"

      :hawkes_bay ->
        "Hawke's Bay"

      :manawatu_wanganui ->
        "Manawatu-Wanganui"

      other ->
        other
        |> Atom.to_string()
        |> String.split("_")
        |> Enum.map_join(" ", &String.capitalize(&1))
    end
  end
sevenseacat
sevenseacat•2mo ago
ahhhh I see, the order of the use statements matter
aidalgol
aidalgolOP•2mo ago
Is that generally considered an anti-pattern?
sevenseacat
sevenseacat•2mo ago
I don't think so. it's not one I tend to use though
Solution
Chaz Watkins
Chaz Watkins•2mo ago
I added some functions to Enum awhile back for this. Pretty sure there are some examples in the docs. https://hexdocs.pm/ash/Ash.Type.Enum.html#module-value-labels-and-descriptions
Chaz Watkins
Chaz Watkins•2mo ago
The label/1 function does the same humanize string behavior as Phoenix.Naming.humanize These are overridable if you need to support translations. Agree we should add something to AshPhoenix for select options.
aidalgol
aidalgolOP•2mo ago
Oh, cool! I missed those in the changelog.

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