aeson

问题 I am new to Haskell, coming from an imperative programming background. I would like to be able to serialize an object to JSON in the "Haskell way", but not quite sure how to do that yet. I have read Chapter 5 of RealWorldHaskell which talks about JSON a bit, and played around with Aeson. I have also looked at a few JSON API libraries written in Haskell, such as: Facebook API in Haskell Stripe API in Haskell That got me to the point of being able to create very basic JSON strings from objects

问题 Toying a bit with the github gist API while trying to get down with the Aeson JSON library. I've run into a problem with the generated ToJSON instance, and I don't know exactly how to solve it. I need to contain a value inside and the key that is associated to the value also needs to be a value and not a predefined key name. It's a bit easier to show. The desired output is, { "public": true, "description": "Something..", "files": {"This Thing.md": {"content": "Here we go!"}} } where the value

问题 I'm a beginner trying to learn more about Haskell and Aeson by parsing some json files I find online. I have a .json that looks like this "Abilities": { "Prime": { "Ammo": 210, "Available": true, "Diposition": 3, "Type": "Secondary", "Class": "Pistols", "NormalAttack": { "Chance": 0.25, "Streak": 2, "Rate": 2.67, "ShotType": "Hit-Scan", "Damage": { "Front": 15, "Back": 15, "Up": 120, "Down": 40 }, "Status": 0.25 } "Accuracy": 9.8, "Reload": 3, "Name": "Prime", "Magazine": 16, }, "Dual": {

问题 I'm a beginner trying to learn more about Haskell and Aeson by parsing some json files I find online. I have a .json that looks like this "Abilities": { "Prime": { "Ammo": 210, "Available": true, "Diposition": 3, "Type": "Secondary", "Class": "Pistols", "NormalAttack": { "Chance": 0.25, "Streak": 2, "Rate": 2.67, "ShotType": "Hit-Scan", "Damage": { "Front": 15, "Back": 15, "Up": 120, "Down": 40 }, "Status": 0.25 } "Accuracy": 9.8, "Reload": 3, "Name": "Prime", "Magazine": 16, }, "Dual": {

问题 I want to create a high-performance HTTP-based API running on Haskell using warp as a HTTP backend. The server shall return JSON data upon request. This data shall be serialized by using Aeson However, warp requires a response object whereas Aeson returns lazy ByteString s. How can I tie both libraries together? For this question's scope I'm not interested in query parsing or routing, but in an example of how to tie both libraries together to deliver a correct JSON with correct headers. Note

问题 If I have an array ["addTask", {"id": "1", "description": "d", "dependsOn": [], "dependentTasks": []}] . data Task = Task { id :: String , description :: String , dependsOn :: [String] , dependentTasks :: [String] } deriving (Eq, Show, Generic, ToJSON, FromJSON) type Change = Storage -> Storage addTask :: Task -> Change addTask (Task id desc dep dept) = insert id (Task id desc dep dept) How can I create a parser that would produce a addTask from that? instance FromJSON (Storage -> Storage)

问题 So happy making it this far, encountered a new hurdle: Got this code made to be encoded to JSON. However no matter when type I use as an instance, the compiler complains. Now I am obviously doing something wrong, but it is exactly what is in the documentation (when using DeriveGeneric obviously). {-# LANGUAGE OverloadedStrings, DeriveGeneric #-} import Data.Aeson import Data.Text as T import Data.ByteString.Lazy as B import Data.ByteString.Lazy.Char8 as BC import GHC.Generics -- decode ::

问题 Trying to do the JSON de-serialisation for a data type with TypeLits, I get stuck with the following problem: Couldn't match type ‘n’ with ‘2’ ‘n’ is a rigid type variable bound by the instance declaration at test.hs:14:10 Expected type: aeson-0.11.2.1:Data.Aeson.Types.Internal.Parser (X n) Actual type: aeson-0.11.2.1:Data.Aeson.Types.Internal.Parser (X 2) How would be the correct syntax to allow Nat generically in the FromJSON instance in the following example: {-# LANGUAGE DataKinds #-} {-#

问题 I'm working with a couple of JSON based APIs and the vast majority of the time I only need to extract a single value from the JSON response. E.g. with {"foo":"xyz","bar":"0.0000012"} I only need the value of bar . To accommodate this I've written functions to extract the information I need: -- | Isolate a Double based on a key from a JSON encoded ByteString isolateDouble :: String -> B.ByteString -> Maybe Double isolateDouble k bstr = isolateString k bstr >>= maybeRead -- | Isolate a String

问题 I'm using Data.Aeson to parse some JSON into a Record type. From time to time data is added to the JSON and this breaks my code as Aeson complains something to the effect of: expected Object with 21 name/value pairs but got 23 name/value I'd really prefer to parse the JSON in a fault tolerant way -- I don't care if more fields are added to the JSON at a later date, just parse whatever you can! Is there a way to achieve this fault tolerance? Here's my code: myRecordFromJSONString :: BS