How to handle effects with Pux? - purescript

Question

I'm just a beginner to the whole world of Purescript and Pux, so I'm a little confused as to where we handle effects.
Currently I'm modelling the effects in my type:
type State = { countries ∷ Maybe (Eff (random :: RANDOM) Countries) }
And then using that in my foldp function:
foldp (Request) state = { state, effects: [countries] }
Where countries is defined as:
countries = do
response <- attempt $ get "/countries.json"
let countries = either (Left <<< show) decode response
pure $ Just $ Receive $ case shuffle <$> countries of
Left _ → Nothing
Right xs → Just xs
However at some point I need to unwrap the RANDOM effect from the type to be able to return it from my view: State → HTML Event.

Answer 1

You simply don't do any side effects in the view. Lift the random effect in your foldp:
data Countries
data Event = Request | Received (Maybe Countries) | FetchError String
type State = {countries :: Maybe Countries, error :: String}
type AppFx fx = (random :: RANDOM | fx)
foldp :: ∀ fx. FoldP State Event (AppFx fx)
foldp (FetchError msg) state = noEffects state{error = msg}
foldp (Received countries) state = noEffects state{countries = countries}
foldp Request state = {state, effects: pure countriesRequest}
where
countriesRequest = Just <$> do
response <- attempt $ getCountries
case response of
Left errorMsg -> pure $ FetchError $ show errorMsg
Right countries -> case shuffle countries of
Left _ -> pure $ Received Nothing
Right shuffleEff -> do
shuffledCountries <- liftEff shuffleEff
pure $ Received $ Just shuffledCountries
shuffle :: ∀ fx. Countries -> Either String (Eff (random :: RANDOM | fx) Countries)
shuffle = unsafeCrashWith "TODO"
getCountries :: ∀ fx. Aff fx Countries
getCountries = unsafeCrashWith "TODO"