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| -rw-r--r-- | doc/design/assistant/blog/day_57__afk/comment_4_8b1f65f141ffd9813e7f5a3380f7f520._comment | 27 |
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diff --git a/doc/design/assistant/blog/day_57__afk/comment_4_8b1f65f141ffd9813e7f5a3380f7f520._comment b/doc/design/assistant/blog/day_57__afk/comment_4_8b1f65f141ffd9813e7f5a3380f7f520._comment new file mode 100644 index 000000000..c87e447d1 --- /dev/null +++ b/doc/design/assistant/blog/day_57__afk/comment_4_8b1f65f141ffd9813e7f5a3380f7f520._comment @@ -0,0 +1,27 @@ +[[!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) + +"""]] |