AF
Ash Framework•5w ago
Rise

pass attribute to expression in calculation

I have the following expression in a calculation. This works if the resource has the attribute starts_at. But how to make this expression generic that any attribute can be used. 
  use Ash.Resource.Calculation

  def expression(_opts, _context) do
    expr(fragment("to_char(?,'DD.MM.YYYY')", starts_at))
  end
  use Ash.Resource.Calculation

  def expression(_opts, _context) do
    expr(fragment("to_char(?,'DD.MM.YYYY')", starts_at))
  end
Ive tried passing :starts_at in opts but with arguments: %{field: :starts_at}. but how it is not clear how to use it 
 calculate :display_starts_at,
              :string,
              {Project.Calculations.FormatDatetime, field: :starts_at}
 calculate :display_starts_at,
              :string,
              {Project.Calculations.FormatDatetime, field: :starts_at}
2 Replies
sevenseacat
sevenseacat•5w ago
it'll be a ref - eg. ref(opts[:field]) I think
Rise
RiseOP•5w ago
yes that works!
I am still a bit shaky when it comes to how and when to use ref,arg, parent and i think there are some more.

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