Printing a wreq response to the terminal

Question

I want to do something very simple; make a wreq response and print the contents to the terminal.

main.hs looks like this: {-# LANGUAGE OverloadedStrings #-}

module Main where

import Network.Wreq
import qualified Data.ByteString.Char8 as C

main :: IO ()
main = do
  r <- get "http://httpbin.org/get"
  putStrLn (C.unpack r)

Why? Because r seems to be a bytestring, so it should be unpackable.

Prelude> import Network.Wreq
Prelude Network.Wreq> r <- get "http://httpbin.org/get"
Prelude Network.Wreq> :type r
r :: Response Data.ByteString.Lazy.Internal.ByteString

My .cabal file looks like this:

executable wreqscraper
  hs-source-dirs:      src
  main-is:             Main.hs
  default-language:    Haskell2010
  build-depends:       base >= 4.7 && < 5,
                       wreq,
                       bytestring

And when I try to build it with stack build I get this:

/Users/mkaravan/end2end/haskell_sandbox/wreqscraper/src/Main.hs:22:22: error:
    • Couldn't match expected type ‘C.ByteString’
                  with actual type ‘Response
                                      Data.ByteString.Lazy.Internal.ByteString’
    • In the first argument of ‘C.unpack’, namely ‘r’
      In the first argument of ‘putStrLn’, namely ‘(C.unpack r)’
      In a stmt of a 'do' block: putStrLn (C.unpack r)

What is the correct way to print these contents with putStrLn (or something similar)?

Answer 1

You need to unwrap the Response ByteString , so you get a ByteString and you can use it with C.unpack .

Here is a working example:

{-# LANGUAGE OverloadedStrings #-}

import Network.Wreq
import Control.Lens
import Data.ByteString.Lazy.Char8 as C

main :: IO ()
main = do
    r <- get "http://httpbin.org/get"
    Prelude.putStrLn $ C.unpack $ (r ^. responseBody)