Unable to trigger response message when sending initial message - elm

Question

I am unable to trigger a response message when sending an initial message.
I have a button:
button
[ class "register"
, value "Create Account"
, onClick Submit
]
I have the following messages:
type Msg
= Submit
| Response (Result Http.Error JsonProfile)
The message handler that is invoked via button click is the following:
update : Msg -> Form -> ( Form, Cmd Msg )
update msg model =
case msg of
Submit ->
( model, runtime.tryRegister model Response )
...
Here's the other message handlers:
update : Msg -> Form -> ( Form, Cmd Msg )
update msg model =
case msg of
Submit ->
( model, runtime.tryRegister model Response )
Response (Ok json) ->
( model, Navigation.load <| "/#/portal/1" )
Response (Err error) ->
( model, Cmd.none )
My tryRegister implementation is the following:
tryRegister : Form -> (Result Http.Error JsonProfile -> msg) -> Cmd msg
tryRegister form msg =
let
jsonProfile =
JsonProfile 1 form.firstName form.lastName form.email
newMsg v =
msg
in
Cmd.map (newMsg <| Result.Ok jsonProfile) Cmd.none
Here's the client code to the elm module depicted above:
onRegistration : Registration.Msg -> Model -> ( Model, Cmd Msg )
onRegistration subMsg model =
let
( form, _ ) =
Registration.update subMsg model.registration
in
case subMsg of
Registration.Submit ->
( { model | registration = form }, Cmd.none )
Registration.Response result ->
case result of
Result.Ok jsonProfile ->
let
newUser =
jsonProfileToProvider jsonProfile
newState =
{ model
| registration = form
, portal =
{ initPortal
| provider = newUser
, requested = Domain.EditProfile
, linksNavigation = False
, sourcesNavigation = False
}
}
in
( newState, Navigation.load <| "/#/portal/" ++ getId newUser.profile.id )
Result.Err _ ->
( model, Cmd.none )
Expectation:
I expect that when I click the button, that navigation takes place.
However, nothing happens and I don't understand why.
Video
Source code is here.

Answer 1

Apparently Cmd.map (...) Cmd.none is not sufficient to force another update cycle. You can force an update cycle by sending an always-succeeding task with Task.perform.
tryRegister : Form -> (Result Http.Error JsonProfile -> msg) -> Cmd msg
tryRegister form msg =
JsonProfile 1 form.firstName form.lastName form.email
|> Result.Ok
|> msg
|> Task.succeed
|> Task.perform identity
Note: There are good reasons not to do this, as outlined here, but we'll ignore those for now to fit the framework you've outlined
However, that alone will not make your code work. You have a nested update call which ignores the Cmd returned from Register.update:
( form, _ ) =
Registration.update subMsg model.registration
That underscore has the effect of blocking all commands generated from the child update. You will need to retain that child Cmd, map it to the parent Cmd, and return it instead of Cmd.none inside all onRegistration cases. For example:
onRegistration : Registration.Msg -> Model -> ( Model, Cmd Msg )
onRegistration subMsg model =
let
( form, subcmd ) =
Registration.update subMsg model.registration
regcmd =
Cmd.map OnRegistration subcmd
in
case subMsg of
Registration.FirstNameInput _ ->
( { model | registration = form }, regcmd )
...

Answer 2

Cmd.none is used in tryRegister function, which does nothing. I think you should use Http.send which actually fires the message loop after the http request completes.
The shortest example...,
update msg model =
case msg of
Submit ->
(model, Http.send Response request)
Response ... ->
...