I want to use the focus library to update a nested property per this
example from the docs
<http://package.elm-lang.org/packages/evancz/focus/2.0.1/Focus>:
set (physics => velocity => x) 0 object
My model is like this:
0 { canvas =
1 { width = 800
2 , height = 600
3 , scale = 1
4 , ratioToWorld = 10
5 }
6 , player = player
7 , enemy = enemy
8 }
My update code is this:
0 update : Msg -> Model -> (Model, Cmd Msg)
1 update action model =
2 case action of
3 Step time ->
4 let
5 newScale = model.canvas.scale + 1
6 newModel = Focus.set (canvas => scale) newScale model
7 in
8 (newModel, Cmd.none)
9 NoOp ->
10 (model, Cmd.none)
Initially I had a great deal of trouble with the compiler complaining about
the "=>" operator but I got lucky and found a code example in github
somewhere that showed me how to import it from the module with this:
0 import Focus
1 import Focus exposing ((=>))
But I'm still getting syntax errors where it complains that it doesn't know
what canvas, scale etc are:
Detected errors in 1 module.
-- NAMING ERROR ------------------------------------------------- ././Update
.elm
Cannot find variable `canvas`
17| newModel = Focus.set (canvas => scale) newScale model
^^^^^^
-- NAMING ERROR ------------------------------------------------- ././Update
.elm
Cannot find variable `scale`
17| newModel = Focus.set (canvas => scale) newScale model
^^^^^
Maybe you want one of the following?
List.scanl
Any help with what I'm doing wrong would be appreciated. I could work how
to do it without using Focus but I plan/hope to use Focus a lot.
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