AE
Ash Elixir•3y ago
cro

Where is the right place to perform transformation on form data before database insert?

Greetings, I have a form that will contain plain text in AsciiDoc format. I would like to convert the AsciiDoc to HTML and store it alongside the original in the database. I'm having a hard time understanding where the best place to do this is. I thought it would be a good candidate for an Ash Calculation, but the examples don't seem to deal with this kind of thing, so I wondered if it was an anti-pattern. In the spirit of "try the simplest thing that will work", I could just do it in the handle_events for creating and updating the resources. Is that a decent approach? Am I overthinking it?
2 Replies
ZachDaniel
ZachDaniel•3y ago
I would suggest doing it in the resource. We have a similar pattern in ash_hq to transform markdown to HTML 
changes do
  change before_action(fn changeset ->
    text = Ash.Changeset.get_attribute(changeset, :text)
    Ash.Changeset.force_change_attribute(changeset, :text_html, to_html(text))
  end), where: [changing(:text)]
end
changes do
  change before_action(fn changeset ->
    text = Ash.Changeset.get_attribute(changeset, :text)
    Ash.Changeset.force_change_attribute(changeset, :text_html, to_html(text))
  end), where: [changing(:text)]
end
You can use a global change to add this behavior to any action that is changing the text attribute. and using before_action there ensures that you don't do an expensive translation on every type of the form It is shorthand for this: 
changes do
  change fn changeset, context ->
    Ash.Changeset.before_action(changeset, fn changeset -> 
      text = Ash.Changeset.get_attribute(changeset, :text)
      Ash.Changeset.force_change_attribute(changeset, :text_html, to_html(text))
    end)
  end, where: [changing(:text)]
end
changes do
  change fn changeset, context ->
    Ash.Changeset.before_action(changeset, fn changeset -> 
      text = Ash.Changeset.get_attribute(changeset, :text)
      Ash.Changeset.force_change_attribute(changeset, :text_html, to_html(text))
    end)
  end, where: [changing(:text)]
end
cro
croOP•3y ago
Great, I will try this. Thank you!

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