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

[Greg Weber]

oh, you are using Maybe- the field needs to be filled in with Nothing

On Thu, Mar 17, 2011 at 7:52 AM, Greg Weber <greg at gregweber.info> wrote:

> 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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