我对 Haskell 比较陌生,现在我正在尝试更深入地了解并尝试习惯不同的流行库。
现在我正在尝试“aeson”。
我想要做的是解析来自的 MSFT 报价请求
这就是它的样子
{
"Global Quote": {
"01. symbol": "MSFT",
"02. open": "105.3500",
"03. high": "108.2400",
"04. low": "105.2700",
"05. price": "107.6000",
"06. volume": "23308066",
"07. latest trading day": "2018-10-11",
"08. previous close": "106.1600",
"09. change": "1.4400",
"10. change percent": "1.3564%"
}
}
这就是我到目前为止所得到的
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}
import Data.Aeson
import qualified Data.ByteString.Lazy as B
import GHC.Exts
import GHC.Generics
import Network.HTTP
import Network.URI
jsonURL :: String
jsonURL = "http://www.alphavantage.co/query?function=GLOBAL_QUOTE&symbol=MSFT&apikey=demo"
getRequest_ :: HStream ty => String -> Request ty
getRequest_ s = let Just u = parseURI s in defaultGETRequest_ u
jsonReq = getRequest_ jsonURL
data Quote = Quote {quote :: String,
symbol :: String,
open :: Float,
high :: Float,
low :: Float,
price :: Float,
volume :: Float,
ltd :: String,
previousClose :: Float,
change :: Float,
changePerct :: Float
} deriving (Show, Generic)
instance FromJSON Quote
instance ToJSON Quote
main :: IO ()
main = do
d <- simpleHTTP jsonReq
body <- getResponseBody d
print (decode body :: Maybe Quote)
我究竟做错了什么?
编辑:答案中的固定版本。