打印一個wreq響應到終端

Question

我想做一些非常簡單的事情； 做出wreq響應，然后將內容打印到終端。

main.hs看起來像這樣：{-＃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)

為什么？ 因為r似乎是一個字節串，所以它應該不可解壓縮。

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

我的.cabal文件如下所示：

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

當我嘗試使用stack build來構建它時，我得到了：

/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)

用putStrLn （或類似方法）打印這些內容的正確方法是什么？

Answer 1

您需要解開Response ByteString ，以便獲得ByteString並將其與C.unpack一起C.unpack 。

這是一個工作示例：

{-# 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)