Elm send message to mailbox in update function [duplicate]

问题

I've the following Action handler in my update function of Elm StartApp MUV framework.

signupAlertMailbox : Signal.Mailbox String
signupAlertMailbox =
  Signal.mailbox ""

update : Action -> Model -> (Model, Effects Action)
update action model =
  case action of
    Submit ->
      let isInputValid = Dict.foldl (\fieldName fieldState validity -> if validity
                                                                then (fieldState == IsOkay)
                                                                else validity)
                                                                True model.inputState
          rnd = log "Input valid" isInputValid
      -- in (model, Effects.none)
      in if isInputValid
            then (model, Signal.send signupAlertMailbox.address "Oh snap! Change a few things up and try submitting again."
                                |> Effects.task
                                |> Effects.map (always Submit))
            else (model, Signal.send signupAlertMailbox.address "Well done! All input correct!"
                                |> Effects.task
                                |> Effects.map (always Submit))

Upon Submit action, I can see the log message in browser console, but no message is being sent to signupAlertMailbox. Please help me with this issue.

-- Edit

The StartApp wiring up code as requested in comment below:

import StartApp exposing (start)
import Time exposing (every, second)

import Pages.Signup.Model
import Pages.Signup.Update exposing (signupAlertMailbox)
import Pages.Signup.View

app =
  start
    { init = Pages.Signup.Model.init
    , view = Pages.Signup.View.view
    , update = Pages.Signup.Update.update
    , inputs = []
    }

回答1:

The reason was I hadnt handed over the app.tasks to a port for it be executed as mentioned by Chad Gilbert @chad-gilbert in a comment above. Thanks!

I added the following section and I started getting those messages in sigupAlertMailbox mailbox from the update function

port tasks : Signal (Task.Task Never ())
port tasks =
  app.tasks

来源：https://stackoverflow.com/questions/34978145/elm-send-message-to-mailbox-in-update-function

标签

elm