Question

这是我在Stack Overflow上的第一篇文章，我对Haskell和编程/ Web开发一般都是新手。我正在使用它来尝试将一些JSON解析为ADT类型。

以下是我想尝试解析的JSON部分：

{"resource":"teamgamelog",
 "parameters":{"TeamID":1610612747,"LeagueID":null,"Season":"2015-16","SeasonType":"Regular Season","DateFrom":null,"DateTo":null},
 "resultSets":[
   {"name":"TeamGameLog",
    "headers":["Team_ID","Game_ID","GAME_DATE","MATCHUP","WL","W","L","W_PCT","MIN","FGM","FGA","FG_PCT","FG3M","FG3A","FG3_PCT","FTM","FTA","FT_PCT","OREB","DREB","REB","AST","STL","BLK","TOV","PF","PTS"], 
    "rowSet": [ [1610612747,"0021501228","APR 13, 2016","LAL vs. UTA","W",17,65,0.207,240,41,85,0.482,6,25,0.240,13,15,0.867,8,39,47,19,6,3,13,17,101]
               ,[1610612747,"0021501209","APR 11, 2016","LAL @ OKC","L",16,65,0.198,240,23,81,0.284,7,31,0.226,26,30,0.867,10,38,48,15,8,1,15,20,79]
               ,[1610612747,"0021501195","APR 10, 2016","LAL @ HOU","L",16,64,0.2,240,41,83,0.494,12,28,0.429,16,19,0.842,7,33,40,25,10,3,18,15,110]
               .
               .
               .
               ]
   }
}

我想要完成的工作最后是[GameResult]，其中每个GameResult都来自JSON "rowSet"密钥中的嵌套数组：

data GameResult = GameResult { team_ID   :: Int
                             , game_ID   :: String
                             , game_date :: String
                             , matchup   :: String
                             , wl        :: Char
                             , w         :: Int
                             , l         :: Int
                             , w_pct     :: Float
                             , min       :: Int
                             , fgm       :: Int
                             , fga       :: Int
                             , fg_pct    :: Float
                             , fg3m      :: Int
                             , fg3a      :: Int
                             , fg3_pct   :: Float
                             , ftm       :: Int
                             , fta       :: Int
                             , ft_pct    :: Float
                             , oreb      :: Int
                             , dreb      :: Int
                             , reb       :: Int
                             , ast       :: Int
                             , stl       :: Int
                             , blk       :: Int
                             , tov       :: Int
                             , pf        :: Int
                             , pts       :: Int
                             } deriving (Show, Eq, Ord, Read)

到目前为止，我有这个：

module Main where

import Data.Aeson
import Network.HTTP.Conduit (simpleHttp)

data RowSet  = ResultSet [GameResult] deriving (Show, Eq, Read)
data ResultSets = ResultSets [RowSet] deriving (Show, Eq, Read)

instance FromJSON ResultSets where
  parseJSON (Object o) = ResultSets <$> (o .: "resultSets")

instance FromJSON RowSetSet where
  parseJSON (Object o) = RowSet <$> (o .: "rowSet")

jsonURL :: String
jsonURL = "http://stats.nba.com/stats/teamgamelog/?Season=2015-16&SeasonType=Regular%20Season&TeamID=1610612747"

getJSON :: IO B.ByteString
getJSON = simpleHttp jsonURL

main :: IO ()
main = do
  d <- (eitherDecode <$> getJSON) :: IO (Either String (Maybe ResultSets)) 
  case d of
    Left err -> putStrLn err
    Right ps -> putStrLn (show ps)

不确定这是否应该是我应该去的方向，但我想到了一个冗长的模式匹配：

instance FromJSON GameResult where
  parseJSON arr = do 
  [a,b,c,...x,y,z] <- parseJSON arr
  GameResult <$> a <*> b <*> c <*> ...

当然，我在尝试编译时遇到了一些错误：

Couldn't match type ‘Int’ with ‘Float’
  Expected type: Parser Float
    Actual type: Parser Int
In the second argument of ‘(<*>)’, namely ‘l’
  In the first argument of ‘(<*>)’, namely
    ‘GameResult <$> a <*> b <*> c <*> d <*> e <*> f <*> g <*> h <*> i
     <*> j
     <*> k
     <*> l’
  In the first argument of ‘(<*>)’, namely
    ‘GameResult <$> a <*> b <*> c <*> d <*> e <*> f <*> g <*> h <*> i
     <*> j
     <*> k
     <*> l
     <*> m’

我在控制台中总共有8个错误。

我很感激我能得到的任何帮助。如果这篇文章有点冗长而且代码不好，我很抱歉。

编辑：事实证明我已经解决了我的问题。感谢jonathan-portorreal和epsilonhalbe，我再次查看了我的类型，并查看了Lens包中的一些想法。我最终在我的do实例中使用了FromJSON GameResult块，但我仍然遇到类型问题，因为事实证明我使用w和l作为某些字段名称GameResult ADT及其之外。

instance FromJSON GameResult where
  parseJSON arr = do 
  [a,b,c,d,...,l,...,w,x,y,z] <- parseJSON arr
  team_ID   <- a
  game_ID   <- b
  game_date <- c
  matchup   <- d
  wl        <- e
  w         <- f
  l         <- g
  ...
            <- l
            ...
            <- w

我绝对会清理它，一旦我更熟悉基础知识，可能会使用Lens包。

如何使用Aeson将多类型数组的JSON解析为自定义Haskell类型？

0 个答案: