Redux-saga inspired library for dealing with I/O in Purescript apps. The idea is to completely isolate all I/O from pure code, meaning that neither the reducer, nor the components, nor the action creators do any kind of I/O leaving the application mostly pure and placing all I/O into a single location.
To do so, purescript-redux-saga creates a virtual thread of execution whose inputs are either actions produced by the UI or attached Sagas, or values received through "channels".
API documentation is published on Pursuit.
-- Types.purs
type GlobalState = {}
data Action
= LoginRequest { username :: String, password :: String }
| LoginFailure Error
| LoginSuccess { username :: String, token :: String }
-- Sagas.purs - Perform *all* I/O your app does here
saga :: ∀ env. Saga env Action GlobalState Unit
saga = forever do
take case _ of
LoginRequest { username, password } -> Just do
liftAff (attempt $ authenticate username password) >>= case _ of
Left err -> put $ LoginFailure err
Right token -> put $ LoginSuccess { username, token }
_ -> Nothing
-- Store.purs - Install the Saga middleware
mkStore
:: ∀ eff
. Eff (ReduxEffect _)
(ReduxStore _ GlobalState Action)
mkStore = Redux.createStore reducer initialState middlewareEnhancer
where
initialState = {}
middlewareEnhancer = Redux.applyMiddleware
[ loggerMiddleware
, sagaMiddleware saga
]
-- Main.purs - Tie the bow
main :: ∀ e. Eff _ Unit
main = do
store <- mkStore
Redux.createProviderElement store [ Redux.createElement_ appClass [] ]For a fully worked example, have a look at purescript-redux-saga-example.