How about modeling your problem differently:
type FieldData
= DropdownField (List String) -- list of choices
| FreeformField
| NumberField Int Int -- min max
type alias Field =
{ name : String
, key : String
, del : Bool
, data : FieldData
}
This way you have easier access to the common fields. :)
On Wed, Jun 22, 2016 at 8:16 PM, Mark Green <[email protected]> wrote:
> Fair enough.
>
> The situation is that as part of the view update, my database model is
> calculating what inputs it needs displayed by passing a form data structure
> to the view component which renders it in HTML. The current type is:
>
> type Field =
> DropdownField { name: String, key : String, choices: (List String),
> del: Bool }
> | FreeformField { name: String, key : String, del: Bool }
> | NumberField { name: String, key: String, min: Int, max: Int, del: Bool
> }
>
> There's two problems. First of all, there's some common validation done
> before any field is displayed involving checking that the key exists in the
> database (which is a Dict) and getting its value. At the moment, in order
> to do that I have to have a function
>
> fieldKey x = case x of
> DropdownField df -> df.key
> FreeformField ff -> ff.key
> NumberField nf -> nf.key
>
> which seems a bit awkward. As I understand it I could use a generic record
> instead by removing the tags on the field types above, but that creates the
> problem that if the function that does the preprocessing accepts the value
> as a generic record { key: String } then it can't call the function to
> render the field because that requires all the components of the record.
>
> The second problem is that "del" field. It represents if the field can be
> deleted or not. It's a pain to have to constantly indicate it when it's in
> practice the same for all fields in any given form, but having to pass the
> form as well as the field to the field renderer is rather awkward, and as I
> understand it Elm doesn't support pointers so I can't put a reference back
> to the parent form in the field object.
>
> Mark
>
> --
> You received this message because you are subscribed to the Google Groups
> "Elm Discuss" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected].
> For more options, visit https://groups.google.com/d/optout.
>
--
There is NO FATE, we are the creators.
blog: http://damoc.ro/
--
You received this message because you are subscribed to the Google Groups "Elm
Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
