使用Aeson将嵌套的JSON解析为元组列表

{-# LANGUAGE OverloadedStrings #-}

import Data.Aeson
import Data.Text (Text)
import qualified Data.ByteString.Lazy.Char8 as B

-- 定义数据类型
data Person = Person
  { name :: Text
  , age :: Int
  } deriving Show

-- 实现FromJSON实例
instance FromJSON Person where
  parseJSON (Object v) = Person
    <$> v .: "name"
    <*> v .: "age"
  parseJSON _ = fail "Invalid Person object"

-- 解析JSON字符串为元组列表
parseNestedJSON :: B.ByteString -> Maybe [(Text, Person)]
parseNestedJSON jsonStr = do
  -- 解析JSON字符串为Aeson的Value类型
  json <- decode jsonStr
  -- 解析嵌套的JSON字段为元组列表
  case json of
    Object obj -> sequenceA $ map parsePerson (toList obj)
    _ -> Nothing
  where
    parsePerson (key, value) = do
      -- 解析嵌套字段为Person类型
      person <- parseJSON value
      return (key, person)

-- 示例JSON字符串
jsonString :: B.ByteString
jsonString = "{\"users\": [{\"name\": \"Alice\", \"age\": 25}, {\"name\": \"Bob\", \"age\": 30}]}"

main :: IO ()
main = do
  let result = parseNestedJSON jsonString
  print result