CODEWITHSUNDEEP
elm
Guilhem Soulas
Guilhem Soulas

Reputation: 1995

Elm: Update a command coming from nested module

In my Elm app, there is a parent and a child. I would like the child to send an HTTP command and then the parent would update it on the fly by adding the backend config that the child model doesn't have.

The way I see it is:

  1. The child sends the HTTP command (update function)
  2. The command is transferred to the parent (update function)
  3. The parent adds the config to command (is this possible??)
  4. The command is finally executed with all the required parameters

I would like to implement HTTP actions in children modules so my app remains modular while keeping the config in one place.

Any help is welcome. Maybe a different approach can solve my problem too!

Upvotes: 2

Views: 996

Answers (1)

pdamoc
pdamoc

Reputation: 2923

Keep all the configuration details in a module that handles the Http Requests. For example, you can have this code in Requests.elm 

import Http
import Task

url = "http://ip.jsontest.com/"


getIP : (String -> msg) -> Cmd msg
getIP tagger = 
  Http.getString url
  |> Task.perform (\e -> tagger (toString e)) tagger

and then in the Component code have something like 

update msg model =
  case msg of 
    GetIP -> model ! [Requests.getIP ShowIP]
    ShowIP str -> {model | ipStr = str} ! []

all the configuration details are hidden from the component. Only an API of access is exposed.

LATER EDIT:

Another option would be to define and pass around a dynamic Context. You can manage this context at the top level and just pass the current version around when you update things. It would look like this

In Requests.elm 

import Http
import Task

type alias Context =
  { url : String }

getIP : Context -> (String -> msg) -> Cmd msg
getIP ctx tagger = 
  Http.getString ctx.url
  |> Task.perform (\e -> tagger (toString e)) tagger

in Components: 

update ctx msg model =
  case msg of 
    GetIP -> model ! [Requests.getIP ctx ShowIP]
    ShowIP str -> {model | ipStr = str} ! []

Upvotes: 2

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