Hi,
I come from an OOP background and trying to make the leap to keeping all
state in a single immutable data store, which has shown to be amazing as
long as the system is small, but I am having trouble scaling up to anything
beyond a toy app.
One big challenge is trying to update nested fields. For example if I want
to change a forecast parameter in the following code:
-- Model
type alias Forecast =
{ parameters: Pf.ArpsParameters
, production: List Float
}
type alias Model =
{ primaryForecast: Forecast
, secondaryForecast: Forecast
}
-- Init
init : (Model, Cmd Msg)
init =
(
{ primaryForecast =
{ parameters =
{ q = Nothing
, de = Nothing
, c = Nothing
, months = [0..48]
}
, production = []
}
}
, Cmd.none
)
I end up with code like this:
update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
let
primaryForecast = model.primaryForecast
parameters = model.primaryForecast.parameters
in
case msg of
Q string -> ({ model | primaryForecast = { primaryForecast |
parameters = { parameters | q = toMaybe (String.toFloat string) } } },
message UpdateProduction)
De string -> ({ model | primaryForecast = { primaryForecast |
parameters = { parameters | de = toMaybe (String.toFloat string) } } },
message UpdateProduction)
C string -> ({ model | primaryForecast = { primaryForecast |
parameters = { parameters | c = toMaybe (String.toFloat string) } }},
message UpdateProduction)
UpdateProduction -> ...
This seems unnecessarily verbose, and I'm unsure whether I am turning wrong
with how I am structuring data or if I am trying to modify data incorrectly.
Thanks for any help!
Austin
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