박준규 @curry@hackers.pub
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‘그냥 tryAny 쓰면 예외는 다 잡을 수 있는 거 아닌가? 왜 ResourceT를 써야 하지?’라고 생각했는데 찾아보니 tryAny로는 비동기 예외를 잡을 수 없다고 한다.

writeGreetingSafeAttempt :: IO ()
writeGreetingSafeAttempt = do
  dir <- getDataDir
  h <- IO.openFile (dir </> "greeting.txt") WriteMode
  _ <- tryAny do
    IO.hPutStrLn h "hello"
    IO.hPutStrLn h "world"
  IO.hClose h

Control.Monad.Trans.Resource

DescriptionAllocate resources which are guaranteed to be released.For more information, see https://github.com/snoyberg/conduit/tree/master/resourcet#readme.One point to note: all register cleanup actions live in the IO monad, not the main monad. This allows both more efficient code, and for monads to be transformed.

hackage.haskell.org

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