[web-devel] when we switch to aeson, perhaps a QQ for JSON..

[Greg Weber]

That seems like a fundamental limitation of haskell records- they aren't
meant to have empty fields. I would create 2 different kinds of messages or
use an alist or a map. Otherwise you could try to wrap the field in a Maybe.

On Thu, Mar 17, 2011 at 7:33 AM, Max Cantor <mxcantor at gmail.com> wrote:

> I think my main issue is that it because it needs a map from json <->
> haskell type, can you have json objects with differing keys?
>
> For instance, say we want to return one of:
> {status: 0, content: "boo.."} and {status: 1, errorMsg: "duck typing is
> bullsh*t"}
>
> with the json library's generic functions you can't do this.  even:
>
> data Msg = Msg { status :: Int, content :: Maybe String, errorMsg :: Maybe
> String }
>
> won't work as it will choke on the "missing" fields.
>
> Max
>
> On Mar 17, 2011, at 10:01 PM, Greg Weber wrote:
>
> > I agree that ToJson as is now is biased towards arrays. I have some code
> like the below now. After we switch over we should make sure it is easy to
> create key-value objects. Perhaps we will need a second ToJson that is
> biased towards key-value objects instead of arrays.
> >
> > documentToJson :: [Field] -> J.Value
> > documentToJson = jsonMap . map toAssoc
> >
> > toAssoc :: Field -> (String, J.Value)
> > toAssoc (l := v) = (unpack l, toJson v)
> >
> >
> >
> >
> > On Wed, Mar 16, 2011 at 11:44 PM, Max Cantor <mxcantor at gmail.com> wrote:
> > ToJson doesn't seem to be able to generate JSON objects (key/value maps).
>  Also, one problem that I've had with other generic JSON libs is that they
> dont give you enough control over the JSON structure.  So, you need to write
> your client code around a particular JSON structure which can be unwieldy at
> times.
> >
> > max
> > On Mar 17, 2011, at 1:37 PM, Greg Weber wrote:
> >
> > > Are you using the ToJson converter? I don't think QQ offers much
> advantage over utilities that can automatically convert haskell data
> structures to JSON. I believe aeson comes with this functionality and also
> some generics functionality if you define a Data instance.
> > >
> > >
> http://hackage.haskell.org/packages/archive/json-enumerator/0.0.1/doc/html/Text-JSON-ToJson.html
> > >
> > > On Wed, Mar 16, 2011 at 8:32 PM, Max Cantor <mxcantor at gmail.com>
> wrote:
> > > I know that the kickass yesod team is looking to change the json
> library to aeson.
> > >
> > > One nice feature would be quasi-quoting for the library like in the
> following library.
> > >
> hackage.haskell.org/packages/archive/text-json-qq/0.2.0/doc/html/Text-JSON-QQ.html
> > > _______________________________________________
> > > web-devel mailing list
> > > web-devel at haskell.org
> > > http://www.haskell.org/mailman/listinfo/web-devel
> > >
> >
> >
>
>
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