2013/2/17 Oliver Charles <ol...@ocharles.org.uk>: > On 02/17/2013 03:01 PM, Sergey Mironov wrote: >> >> Hi folks. Hackage contains several JSON packages but as far as I see, >> they all provide 'static' conversion from JSON format to Haskell data >> type. Is there a method of converting object containing optional filed >> 'a' to for example Maybe a. > > Assuming you have some sort of 'path' to the key in question, aeson-lens > might be exactly what you want: > http://hackage.haskell.org/package/aeson-lens > > I use aeson-lens to turn a list of strings of the form ["foo", "bar", "baz"] > into a query into first the 'foo' object, then the 'bar' object, then the > 'baz' object, using the following: > > pathToLens :: Functor f > => [T.Text] > -> (Maybe Value -> f (Maybe Value)) > -> Maybe Value > -> f (Maybe Value) > pathToLens [p] = key p > pathToLens ps = let ps' = filter (not . T.null) ps > in key (head ps') . (foldl (.) id . map pathElem $ tail ps') > where > pathElem p = maybe (key p) nth (readMay $ T.unpack p) > > So as you can see - I turn any arbitrary path into a query into JSON, with a > chance of failure. > > Hope this helps! > - Ollie > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe
Good news, thanks a lot! Sergey _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
