Wai与经纱结合使用MySQL

Question

我想知道下面是否是将Wai与数据库池相结合的正确约定。

我基本上要做的是，创建一个池，部分应用Pool -> Application类型的函数，并使用它将其传递给Warp的run。它看起来还好吗，还是我来重构它？

{-# LANGUAGE OverloadedStrings #-}
import Network.Wai
import Network.HTTP.Types
import Network.Wai.Handler.Warp (run)
import Database.MySQL.Simple
import Data.Pool (Pool, createPool, withResource)

newConn = connect defaultConnectInfo 
    { connectHost = "db"
    , connectUser = "root"
    , connectPassword = "secret"
    , connectDatabase = "test" }

getPool = createPool newConn close 1 10 5

app :: Pool Connection -> Application
app pool _ respond = do
    withResource pool $ \c -> query_ c "SELECT 1" :: IO [Only Int]
    respond $ responseLBS
        status200
        [("Content-Type", "text/plain")]
        "Hello, Web!"

main :: IO ()
main = do
    putStrLn $ "http://localhost:8080/"
    pool <- getPool
    run 8080 $ app $ pool

Answer 1

恐怕没有什么可移除的了。$在putStrLn之后以及app和pool之间是多余的。您可以编写最后两行run 8080 . app <$> getPool。我会给getPool打个内联。您可能对https://github.com/alevy/simple/blob/master/simple/src/Web/Simple.hs#L134的样板还原感兴趣。