Question

我正在使用Control.Monad.Managed将pipes-http的{{1}}包装在一个连续变换器中，但我还想在之后流式传输HTTP响应：

withHTTP

此处import Pipes import Pipes.ByteString import Pipes.HTTP import Control.Applicative import Control.Monad import Control.Monad.Managed import qualified Data.ByteString.Char8 as BC type RespBody = BC.ByteString managedHTTP :: Request -> Manager -> Managed (Response (Producer RespBody IO ())) managedHTTP r m = managed (withHTTP r m) fromHTTP :: Request -> Manager -> Producer RespBody IO () fromHTTP request manager = join $ liftIO $ fmap (hoist liftIO) $ with response return where response = responseBody <$> managedHTTP request manager旨在流出响应正文。如果以上运行：

fromHTTP

我在第一个块之后得到main = do request <- parseUrl "http://en.wikipedia.org/" manager <- newManager defaultManagerSettings runEffect $ fromHTTP request manager >-> stdout，因为recv: invalid argument (Bad file descriptor)的{{1}}已经关闭了我的回复正文。

如果我想公开非http-client样式的界面，我应该如何使用管道传输HTTP响应？

谢谢＆amp;如果我严重误解延续和管道，请道歉。

Answer 1

您对fromHTTP的定义有点难以理解，但它显然让您在实际开始使用生产者之前退出托管环境。这样的事情可能更接近你的意图：

import Pipes
import Pipes.ByteString
import Pipes.HTTP
import Control.Applicative
import Control.Monad
import Control.Monad.Managed
import qualified Data.ByteString.Char8       as BC

type RespBody = BC.ByteString

managedHTTP :: Request -> Manager -> Managed (Response (Producer RespBody IO ()))
managedHTTP r m = managed (withHTTP r m)

managedManager :: ManagerSettings -> Managed Manager
managedManager settings = managed (withManager settings)

main = runManaged $ 
  do request <- liftIO $ parseUrl "http://en.wikipedia.org/" 
     manager <-  managedManager defaultManagerSettings
     producer <- managedHTTP request manager
     liftIO $ runEffect $ responseBody producer >-> stdout

或者只是废弃定义并写下

main = runManaged $ 
  do request  <- liftIO $ parseUrl "http://en.wikipedia.org/" 
     manager  <- managed (withManager defaultManagerSettings)
     producer <- managed (withHTTP request manager)
     liftIO $ runEffect $ responseBody producer >-> stdout

请注意，您也可以让生产者在Managed monad中运行：

main = runManaged $ 
  do request  <- liftIO $ parseUrl "http://en.wikipedia.org/" 
     manager  <- managed (withManager defaultManagerSettings)
     producer <- managed (withHTTP request manager)
     runEffect $ hoist liftIO (responseBody producer) >-> stdout

从`管理'管道流

1 个答案: