[Haskell-cafe] "Flatten" JSON objects under toListOf

[Daniel Gorín]

I would just write a parser that picks the fields you want. You could have the parser return a Value but I’d rather collect them in a separate data-structure. For your example, one would have:

flatten :: Value -> Either String Value
flatten
  = fmap reencode . parseEither extract
  where
    extract
      = withObject "my obj" $ \o -> do
          dv <- o .: "Dimensions"
          flip (withObject "dim") dv $ \d ->
            liftA2 (,) (o .: "Name") (d .: "W")

    reencode :: (Text,Int) -> Value
    reencode (n,w)
      = object [ "Name" .= n, "W" .= w ]

Now you can map the flatten function over your list of of objects, find out those that were malformed, etc.


On 25 Nov 2014, at 04:41, Stuart Popejoy <spopejoy at panix.com> wrote:

> Hi,
> 
> I'd like to transform some JSON to "flatten" objects in a list to a single dimension. Say I have:
> 
> [{ "Name": "Stuart", "Dimensions": { "H": 71, "W": 170 } },
> { "Name": "Sam", "Dimensions": { "H": 72, "W": 180 } }]
> 
> How do I get it to just
> 
> [{ "Name": "Stuart", "W": 170 } },
> { "Name": "Sam", "W": 180 } }]
> 
> I've tried zipWith with various toListOf constructions to pick apart and rebuild a new JSON object. Is there a better way?
> 
> Thanks,
> Stuart
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