Sending json through port

Learn
1

Hello, first time elm user here.

I am trying to create a program that encodes some parking spot data as json and sends it through a port.

The example in the docs mention cache (E.int 42) where cache is the name of the port.

I tried to modify this slightly, my port is named spotter, but when i compile i get the following error:

Something went wrong while parsing spotter's definition.

46| spotter jason
47| 
48| main =
    ^
I was expecting to see the rest of spotter's definition. Maybe you forgot some
code? Or maybe the body of `spotter` needs to be indented?

Program is here:

port module Main exposing (..)
import Json.Encode as E
import Html as H
import Browser

-- PORTS

port spotter : E.Value -> Cmd msg

-- PARKING INFO

type alias State =
  { string : String
  , bool : Bool
  }

type alias Spot =
  { id : Int
  , longitude : Float
  , latitude : Float
  , available : State
  }

-- ENCODERS

encodeSpot : Spot -> E.Value
encodeSpot spot =
  E.object
  [ ("id", E.int spot.id)
  , ("longitude", E.float spot.longitude)
  , ("latitude", E.float spot.latitude)
  , ("available", encodeState spot.available)
  ]

encodeState : State -> E.Value
encodeState state =
  E.object
  [ ("string", E.string state.string)
  , ("bool", E.bool state.bool)
  ]

testState = State "free" True
testSpot = Spot 55 3.3 3.3 testState
jason = encodeSpot testSpot

-- send through port
spotter jason

-- placeholder main
main =
  H.text testSpot.available.string

What is wrong?

2

Sending data to a port is a command. You probably want to do this in your update or init function. If you’re unfamiliar with commands, check out https://guide.elm-lang.org/effects/

The code will probably look something like:

update : Msg -> State -> (State, Cmd Msg)
update msg state =
  case save of
    SaveState ->
       (model, spotter (encodeState state))
3

It looks like you are trying to use Elm as an imperative language. In elm, you cant just have it run something by calling a function outside of a function definition. If you want to actually be able to do something in your program, you cant use static html as your main value

4

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.