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http://claimid.com/strager 2012-08-11 16:08:47 +00:00 committed by admin
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[[!comment format=mdwn
username="http://claimid.com/strager"
ip="173.228.13.253"
subject="comment 4"
date="2012-08-11T16:08:47Z"
content="""
> How to cancel download? Depends on its implementation .... So it's an abstraction layer violation problem.
Precisely why I suggested returning something as generic as `IO ()`:
-- Current
download :: URLString -> Headers -> [CommandParam] -> FilePath -> IO Bool
-- Suggestion
data Transfer a = Transfer { run :: IO a, cancel :: IO () }
download :: URLString -> Headers -> [CommandParam] -> FilePath -> Transfer
transfer <- download ...
-- You can pass `cancel transfer` to another thread
-- which you want to be able to cancel the transfer.
run transfer -- blocking
I realized while writing this that you may not get any result from e.g. a download while it is occurring (because the function is blocking). Maybe that's where a misunderstanding occurred. I separated the concepts of creating a transfer and starting/canceling it.
(My idea is starting to feel a bit object-oriented... ;P)
"""]]