Parsing JSON data from a URL in Haskell using Aeson -


i'm trying create web app in haskell takes json input url.

{-# language overloadedstrings, derivegeneric #-}  import data.aeson q import data.text import control.applicative import control.monad import qualified data.bytestring.lazy b import network.http.conduit (simplehttp) import ghc.generics --import data.datetime  data temperatures =    temperatures { date :: string                , temperature :: int                  } deriving (show, generic)  instance fromjson temperatures instance tojson temperatures   jsonurl :: string jsonurl = "http://www.phoric.eu/temperature"  getjson :: io b.bytestring getjson = simplehttp jsonurl   main :: io () main =   d <- (eitherdecode <$> getjson) :: io (either string temperatures)  case d of   left e   -> putstrln e   right stuff -> print stuff

however, i'm getting error @ runtime:

bradley$ runhaskell test.hs key "date" not found

the json below @ url in code.

{"temperatures":[     {"date":"2015-02-28t20:16:12+00:00", "temperature":0},     {"date":"2015-01-01t21:46:55+00:00", "temperature":2},      {"date":"2015-04-08t21:46:53+00:00", "temperature":3},     {"date":"2015-04-09t21:46:01+00:00", "temperature":4},     {"date":"2015-04-10t21:46:40+00:00", "temperature":5},     {"date":"2015-04-11t21:46:36+00:00", "temperature":6},     {"date":"2015-04-12t20:36:25+00:00", "temperature":7} ]}

i have no idea why not recognising keys when they're present in json object, ideas?

in current form, code can parse single line of form {"date":"2015-04-12t20:36:25+00:00", "temperature":7} : tries parse input temperatures, can't find date key root object because has temperatures key.

the problem temperatures datatype not match input. here should match:

data datapoint = datapoint { date :: string                            , temperature :: int                            } deriving (show, generic)  data temperatures = temperatures { temperatures :: [datapoint]                                  } deriving (show, generic)

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