In terms of sending an HTTP request when navigating to the Login page, you
should be able to do that by returning an Http Cmd in your `update`
function.
Elm's Navigation library provides a special `program` function which--in
addition to the standard init/update/view/subscription functions used by
Html.program--also takes a function from `Navigation.Location` to a
message that your update function can understand. In the example program
included in the Navigation library, this function is called `UrlChange`.
So in your `update` function, you probably already have a case that listens
for this `UrlChange` message, computes a "route" from the `Location`
attached to this message, and stores the new route in your model.
update msg model =
case msg of
UrlChange location ->
( { model | route = routeFromLocation location }
, Cmd.none
)
All you need to do is change this case so that in addition to returning the
updated model, it looks at the new route and returns a Cmd based on whether
the new route is Login or not.
e.g.
update msg model =
case msg of
UrlChange location ->
let
newRoute =
routeFromLocation location
newCmd =
case newRoute of
Just (Route.Login) ->
Http.get "/api/loginStuff" stuffDecoder
|> Http.send GotStuff
_ ->
Cmd.none
in
( { model | route = newRoute }
, newCmd
)
On Sunday, February 5, 2017 at 11:51:03 AM UTC-8, Kingsley Hendrickse wrote:
>
> Hi,
>
> I'm new to elm and am using version 0.18
>
> I'm struggling a bit to get what I want out of the Route and Navigation
> libraries.
>
> I have 2 features Login and Registration
>
> In the Main.elm I use an update which delegates to either the Login or
> Registration features and then updates the main model after Login or
> Registration has done its thing.
>
> However I want to be able to detect when I'm going to show the Login view
> and before the view is rendered fire off an http request which will be used
> to populate the view. I can't see how to do this. It's easy to do as a
> result of something like a button click - because then the trigger point is
> the button click. But I want the trigger point to be during navigation so
> that the user can arrive on a page and that initial arrival on the page
> triggers the http requests that will be used in that view.
>
> Also if anyone could point me in the direction of a good pattern for
> protecting routes that would be great - e.g. if a user is not logged in
> they should not be allowed to go to the welcome page and get redirected to
> login, and if logged in they should be redirected to welcome and not
> allowed on login or registration etc ...
>
> Any help appreciated
>
> Thanks
>
> --Kingsley
>
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