[Haskell-beginners] Fwd: Can i define a record without defining access method.

9 Jul 2011


      I've never used the main aeson library, but I just tried the aeson-qq
library and got this without any real problem.  Try this:

{-# LANGUAGE QuasiQuotes, TemplateHaskell, DeriveDataTypeable #-}
import Data.Text
import Data.Aeson
import Data.Aeson.QQ
import Data.Aeson.Generic
import Data.Aeson.Types

myReq = [aesonQQ| {age: <|age|>, version: <|version|>} |]
 where age = 34 :: Integer
       version = "1.2"

myResp = [aesonQQ| {age: <|name|>, version: <|version|>} |]
 where name = "harold"
       version = "1.3"
...
encode $ Data.Aeson.Generic.toJSON myReq
Chunk "{\"age\":34,\"version\":\"1.2\"}" Empty
encode $ Data.Aeson.Generic.toJSON myResp
Chunk "{\"age\":\"harold\",\"version\":\"1.3\"}" Empty
On Sat, Jul 9, 2011 at 12:41 PM, yi huang  wrote:
...
On Sun, Jul 10, 2011 at 12:25 AM, Chaddaï Fouché 
wrote:
...
On Sat, Jul 9, 2011 at 5:59 PM, yi huang  wrote:
...
 On Sat, Jul 9, 2011 at 6:45 PM, Tom Murphy  wrote:
...
On 7/9/11, yi huang  wrote:
...
I'm trying to create a haskell implementation of json rpc, I try to
define
protocol using record like this:
data Request = Request {
    version :: Integer
  , id      :: Integer
  , method  :: String
  , args    :: [Value]
} deriving (Typeable, Data, Show)
...
so i can use json library to encode/decode it.
But this code fails, because haskell will define access function
automaticlly, and function names conflicts.
My question is, is there a way i can define record without access
function,
so i can have same attribute name in multiple record.
If you really want to keep those attribute names exactly, you'll have
to check where the conflict is and find a way not to import the
conflicting function name. Here I guess "id" is the big problem since
it comes with the prelude you'll have to use the NoImplicitPrelude
extension and explicitly "import Prelude hiding (id)", I suggest you
make a separate module for your type definition so you don't have to
worry about that in the rest of your code.
Sorry i don't describe my problem well, actually i have two records, Request
and Response, some attributes have same names, e.g. version, id.
data Request = Request {
    version :: Int
    ...
}
data Response = Response {
    version :: Int
    ...
}
And yes, i really want to keep those names exactly, so aeson can
automatically encode them to right json object.
If there are no way to hide access function, then i guess i have to define
them in seperate module, or define them as normal data constructor with
encode/decode precedure defined manually. Both is not pleasant to me.
...
--
Jedaï
--
http://www.yi-programmer.com/blog/
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[Haskell-beginners] Fwd: Can i define a record without defining access method.

David McBride