Acess a servant server with a reflex-dom client

Question

I\'m using version 0.4 of reflex-dom and I have a tiny reflex-dom client:

{-# LANGUAGE OverloadedStrings #-}
import Reflex.Dom
import qualified Data.Text as         


        

Answer 1

You probably are seeing Cross-Origin Resource Sharing (CORS) problems. You can verify this (in chrome at least) by checking your browser console for an error that looks like this:

XMLHttpRequest cannot load http://localhost:8080/name/3. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8000' is therefore not allowed access.

If this is the case, you can enable CORS in your server by replacing this line :

app = serve userAPI server

with this line:

app = simpleCors (serve userAPI server)

You will need to import wai-cors:

import Network.Wai.Middleware.Cors

here is your servant server with these changes:

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeOperators #-}

import Servant
import Servant.API
import Servant.Server
import Network.Wai
import Network.Wai.Handler.Warp
import Network.Wai.Logger       (withStdoutLogger)
import Network.Wai.Middleware.Cors
import qualified Data.Text as T

main :: IO ()
main = withStdoutLogger $ \aplogger -> do
         let settings = setPort 8080 $ setLogger aplogger defaultSettings
         runSettings settings app

app :: Application
app = simpleCors (serve userAPI server)

userAPI :: Proxy API    -- API usage:  http://localhost:8080/name/2
userAPI = Proxy

type API = "name" :> Capture "pid" Int :> Get '[PlainText] T.Text

server :: Server API
server =  name

name :: Monad m => Int ->  m T.Text
name pid = return $ nameById pid

nameById :: Int -> T.Text
nameById 1 = "Isaac Newton"
nameById 2 = "Galileo Galilei"
nameById 3 = "Marie Curie"
nameById _ = "UNKNOWN!!"