I have the following Elm code:
tomorrowTasks : WebData (List Task) -> Html Msg
tomorrowTasks response =
div []
[ maybeList response
, span [ hidden ( model.showNewTaskLoader == False ) ]
[ indeterminateLoader ]
]
maybeList and indeterminateLoader are just some other view elements.
Whenever I change model.showNewTaskLoader in my update-Function, I can see that model.showNewTaskLoader is indeed changing (via the explore history overlay from elm-reactor). However the indeterminateLoader stays hidden.
Why is the DOM not updating the visibility of the element?
Related
Can't quite figure out how to go about sending messages between modules when working with reusable components.
I have an expanding text area that I'd like to use on a number of different sections on a site. The Text Area accepts a portion of HTML that makes up the user actions. Typically handling submit, cancel, upload icons, etc..
Tried to write up a quick example of what I'm talking about without throwing a ton of code on here. So essentially, I'd like to just plug and play peices of HTML that are already attached.
I'm assuming CancelNote is getting fired as a TextArea msg, so it never sees a Cancel Note msg. Not sure how I would use Html.map here (or even if I would).....feel like plug and play method is probably a bad approach, but not sure how else I could achieve decent reusability .
SEPERATE MODULE
update model msg =
case msg of
CancelText ->
( { model | note = (Just "") }
, Cmd.none
)
view: stuff
view stuff =
......
TextArea.view
(button [ Html.Events.onClick CancelText] [])
TEXT AREA MODULE
view : Html.Html msg -> Html msg
view actionHtml =
div [ class "extended_text_area_container" ] [
textarea [] [
]
, actionHtml
]
Messages are just values like any other. You can pass them around directly:
-- SEPERATE MODULE
view: stuff
view stuff =
......
TextArea.view CancelText
-- TEXT AREA MODULE
view : msg -> Html msg
view msg =
div [ class "extended_text_area_container" ]
[ textarea [] []
, button [ onClick msg ] []
]
Edit: If you need to also maintain internal state, just use another message to tell the parent to update the state:
-- Main module
type msg =
...
SetTextAreaState TextArea.state
update model msg =
case msg of
...
SetTextAreaState state ->
{ model | textAreaState = state }
view : Model -> Html msg
TextArea.view SetTextAreaState model.textAreaState
-- TextArea module
type State =
...
type Msg =
Clicked
update : State -> Msg -> State
update state msg =
case msg of
Clicked ->
{ state | clicked = True }
view : (State -> msg) -> State -> Html msg
view toMsg state =
let
updateAndWrap msg =
toMsg (update state msg)
in
div [ class "extended_text_area_container" ]
[ textarea [] []
, button [ onClick (updateAndWrap Clicked) ] []
]
Here, instead of passing a msg to onClick directly in TextArea.view, call a function that updates the state and then wraps it in the msg constructor passed in from the parent, which will produce a message of a type that we don't know anything about.
Also, while I use an internal Msg type and update function similarly to the overall Elm architecture, that is in no way mandatory. It's just a nice way of doing it since it's familiar and scales well.
We can use Html.Lazy.lazy to precisely tag the stateful element, but nothing like Attribute.lazy is avaialbe to tag the stateful attribute. What are the rationals behind this?
type alias Model =
{ text : String, color : String }
view model =
div [ style "color" model.color ]
[ lazy text model.text ]
After reading Elm lazy guide again, I see it was my own misinterpretation about how Html.Lazy really works. Below shows how to tag the model including the stateful attribute.
type alias Model =
{ txt : String, color : String }
viewStateful txt color =
div [ style "color" color ]
[ text txt ]
view model =
lazy2 viewStateful model.txt model.color
I have a hierarchy represented in a couple of dropdowns.
The parent dropdown selection drives the options of the children dropdown when an item is selected.
When a parent is selected, I am populating the children dropdown adding the first element to be blank ("") and display text to be "--select--".
I want this item to be the selected by default in the children's dropdown whenever the parent changes.
The problem is, the "selected" attribute does not seem to be doing its job.
childOptions : String -> Html msg
childOptions val =
-- This selected attribute does not seem to work
Html.option [ (Html.Attributes.selected (val == "")), Html.Attributes.value val ] [ Html.text val ]
You can see the behaviour here:
Ellie editor example
Select parent "entry 1" and then select child "1.2".
Now select parent "entry 2" and notice that it is ignoring the "selected" attribute, which is only true if the child entry is blank ("").
The entry selected by default now is "2.2" which to me indicates it is keeping the position of the previously selected element "1.2".
Any ideas as to who this can be fixed?
The problem appears to lie in the getOptions function; because the arguments to it do not change, its output (per <option> element) also will not change. And since the output does not change, Elm will not modify the selected property of the <option> elements.
(Since there's no Msg event for that <select>, Elm doesn't see the change events and the new value.)
getOptions : String -> Html msg
getOptions val =
Html.option
[ Html.Attributes.selected (val == "")
, Html.Attributes.value val
]
[ Html.text val ]
Each Hierarchy item should track it's selected value, and pass that to getOptions. Something like this:
getOptions : String -> String -> Html msg
getOptions selectedValue val =
Html.option
[ Html.Attributes.selected (val == selectedValue)
, Html.Attributes.value val
]
[ Html.text val ]
I have a feature called Editor that I'm trying to plug into my app. Its view returns a the type Html EditorMsg. I plug it in here:
edit : Editor.Types.Model -> Html EditorMsg
edit editorModel =
div [ class "edit" ] [ Editor.view editorModel ]
In the app, I have routing and so edit is called by way of my main view function, plus a couple of functions that manage which route to show:
-- VIEW
view : Model -> Html Msg
view model =
div []
[ RoutingMsg navBar
, EditorMsg (render model)
]
render : Model -> Html EditorMsg
render model =
case model.route of
Nothing ->
li [] [ text "Invalid URL" ]
Just route ->
showRoute route model
showRoute : Route -> Model -> Html EditorMsg
showRoute route model =
case route of
Home ->
home
Editor ->
edit model.editor
My view also contains a navBar as you can see, and that returns Html possibly containing a different type of message, RoutingMsg:
navBar : Html RoutingMsg
navBar =
NavBarState.config
|> NavBarState.items
[ navItem "/" "Home" False
, navItem "/editor" "Edit" False
]
|> NavBar.view
This setup didn't compile because in view I have a list of two different types, one returning Html RoutingMsg and the other Html EditorMsg, so I set up a union type to try to contain that difference:
type Msg
= RoutingMsg (Html RoutingMsg)
| EditorMsg (Html EditorMsg)
This seems to work, but then I run into trouble in my update method, where the matching doesn't quite work. Long and short of it is that it feels as though I've just got the wrong pattern. My goal was to make my Editor somewhat independent, like a module, that can be plugged in different places. But it's hard for me to understand in Elm, how to integrate things.
To illustrate the problem more simply, I created this example on ellie-app that approximates what I tried to do but can't get working: https://ellie-app.com/PKmzsV3PC7a1/1
Is my approach here just incorrect, or if not, how can I get this code to work?
You should use Html.map to map children messages to the top-level Msg
Here's what you've been missing:
view : Model -> Html Msg
view model =
div []
[ Html.map ButtonDecMsg buttonDec
, div [] [ text (toString model) ]
, Html.map ButtonIncMsg buttonInc
]
Also the type annotation definition of child update functions should include the message type:
buttonDecUpdate : ButtonDecMsg -> Model -> Int
buttonDecUpdate msg model =
model - 1
Here is an example of working app: https://ellie-app.com/PM4H2dpFsfa1/0
I have implemented the HTTP service request using elm architecture.but i am also want to implement any loading gif image so that user will know that something is happen in the back ground.
can any please help me to implement to this implementation.
You can add a property in your model, whether it is loading or not.
Then you can let your view reflect the status by show spinner or text, or whatever.
In case of the example at http example, you can modify
following code, for example by adding iswaiting property in the Model ...
In this example, FetchSucceed message gets fired when ajax call is complete.
type alias Model =
{ topic : String
, gifUrl : String
, iswaiting : Bool
}
update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
case msg of
MorePlease ->
({ model | iswaiting = True }, getRandomGif model.topic)
FetchSucceed newUrl ->
(Model model.topic newUrl False, Cmd.none)
FetchFail _ ->
(model, Cmd.none)
view : Model -> Html Msg
view model =
div []
[ h2 [] [text model.topic]
, text <| if model.iswaiting then "waiting" else ""
, button [ onClick MorePlease ] [ text "More Please!" ]
, br [] []
, img [src model.gifUrl] []
]
You'll have to adjust other parts as well.
But, I hope you can see what is going on.
You can add a loading gif image on body and make it appear on top of the page by z-index and after http request is completed then delete that image from body.