Op maandag 10 oktober 2016 14:58:56 UTC+2 schreef Ambrose Laing:
>
> I would modify the model to also contain a name, description and price, at
> the top level. These are uncommitted values. By uncommitted I mean that
> it should be possible to change any one of these without changing the
> others, and yet your master list of all the items will not change because
> you have not clicked the Run button yet. This is because naturally it is
> impossible to change all three items at once. You change one, and you need
> somewhere to hold the value you have changed while you modify the next one,
> but before you commit a group of three of them as one article into your
> master list.
>
So your model would then look something like this:
type alias Model =
{ articles : List Article
, newName : String
, newDescription : String
, newPrice : String
}
Your update would then include something like:
case msg of
UpdateName inputString ->
{ model | newName = inputString }
UpdatePrice inputString ->
-- etcetera
Also, probably good to render these values in your view too:
[ input [ type' "text", placeholder "Enter a name...", onInput UpdateName,
value model.newName ][]
It is only when you click Run that these three values are copied into an
> Article and the article is appended to the List of articles in your model.
>
And the update for Run then becomes something like
case msg of
Run ->
let
newID =
List.map (.id) model.articles -- get all IDs from the article list
|> List.maximum -- extract the maximum value (this is a Maybe type,
because the list could be empty)
|> Maybe.withDefault 0 -- so give it a default value of 0
newArticle = { id = newId, name = model.newName, ... (etcetera) }
in
{ model
| articles = newArticle :: model.articles
, newName = "" -- reset the input fields after adding
, ... (etcetera)
}
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