envelope

Defines generic 'Envelope' type to wrap reponses from a JSON API. https://github.com/cdepillabout/envelope#readme

LTS Haskell 9.1:0.2.2.0
Stackage Nightly 2017-08-17:0.2.2.0
Latest on Hackage:0.2.2.0
BSD3 licensed by Dennis Gosnell
Maintained by cdep.illabout@gmail.com

Module documentation for 0.2.2.0

There are no documented modules for this package.

Web.Envelope

Build Status Hackage Stackage LTS Stackage Nightly BSD3 license

This module exports an Envelope type that can be used to wrap reponses from a JSON REST API. It provides a successful Success response, and a failure Err response.

Here is a small demonstration of returning a success response:

>>> import qualified Data.ByteString.Lazy.Char8 as C8
>>> import Data.Aeson (decode, encode)
>>> let successEnvelope = toSuccessEnvelope 3 :: Envelope Text Int
>>> C8.putStrLn $ encode successEnvelope
{"data":3}
>>> decode "{\"data\":3}" :: Maybe (Envelope Text Int)
Just (EnvelopeSuccess (Success 3))

Your data gets wrapped in an object with a single "data" field:

{
    "data": 3
}

Now lets look at how an error response is encoded and decoded. It is encoded as an object with two members: @\"extra\"@ and @\"error\"@.

>>> let errorEnvelope = toErrEnvelope "DB_ERROR" "there was an error in the database" :: Envelope String Int
>>> C8.putStrLn $ encode errorEnvelope
{"extra":"there was an error in the database","error":"DB_ERROR"}
>>> decode "{\"extra\":\"there was an error in the database\",\"error\":\"DB_ERROR\"}" :: Maybe (Envelope String Int)
Just (EnvelopeErr (Err {errErr = "DB_ERROR", errExtra = Just "there was an error in the database"}))

Your error type and extra message get wrapped in an object:

{
    "extra": "there was an error in the database",
    "error": "DB_ERROR"
}
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