Computed field based on elixir code instead of SQL

[phortx]

Hi,

I'm currently migrating from Kaffy. I have several calculated fields, which base on business rules that are implemented in elixir. Kaffy supports this via passing a lambda to value.

As far as I understand, computed fields in Backpex are currently only possible via select: dynamic() which extends the query.
Is there also a way to display a computed field based on elixir code? For example:

def fields do
  [
    free_percent: %{
      module: Backpex.Fields.Value,
      label: "Free usage this month",
      select: fn user -> to_string(Subscriptions.determine_quota(user).free_percent <> "%") end
    },
  ]
end

[Flo0807]

Hey,

the easiest way to achieve this is by defining a custom render function.

def fields do
  [
    free_percent: %{
      module: Backpex.Fields.Text,
      label: "Free usage this month",
      render: fn assigns ->
        # user = ...
        free_percent = Subscriptions.determine_quota(user).free_percent <> "%"
        
        assigns = assign(assigns, :label, free_percent)
        
        ~H"""
        <p><%= @label %></p>
        """
      end
    },
  ]
end

in the custom render function, you have the flexibility to display whatever value you want to show.

Note that it sometimes may be better to use the select: dynamic() option because then your field can be orderable and searchable. In the above example, you'd have to turn orderbale to false because the ordering on database level would not make sense.

[phortx]

That's what I've been looking for, thanks!