Haskell, Posting Values to Webpage

Question

I'm trying to figure out how to perform GET's and POST's to websites in Haskell, and I seem to be having difficulty even figuring out how to do a simple POST. I'm sure this is a GET.

import Network.HTTP.Conduit
import Data.Conduit
import Data.Conduit.Binary (sinkFile)
import qualified Data.ByteString.Lazy as L
import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Resource (runResourceT)

main :: IO ()
main = do
  runResourceT $ do

    case parseUrl"https://www.google.com" of
      Nothing -> liftIO $ putStr "Not a valid URL"
      Just req -> withManager $ \manager -> do
        res <- httpLbs req manager
        liftIO . L.putStr $ responseBody res

Can some one please show me an example of how to do a POST in haskell. I have tried to find a good example somewhere that I can understand but haven't had any luck! Can you please show me by using the Post Values "login" -> "James", "Pass" -> "MyPassword". Thanks in advance!

Answer 1

You need to change the Request data type to indicate that it is a POST method call. Also make sure that you have the latest http-client (version 0.3.6) installed as Michael Snoyman has added the setQueryString function quite recently.

{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Conduit
import Control.Monad.IO.Class
import qualified Data.ByteString.Lazy as L
import Control.Monad.Trans.Resource

main :: IO ()
main = do
  runResourceT $ do
    initReq <- parseUrl"https://www.google.com"
    let req = initReq {
          method = "POST"
          }
        req' = setQueryString [("login", Just "James"),("Pass", Just "MyPassword")] req

    withManager $ \manager -> do
      res <- httpLbs req' manager
      liftIO . L.putStr $ responseBody res