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使用Snap开发Web应用程序时,我遇到了模糊类型的问题。Haskell Snap:query_ trouble
我的代码是
getUserByUsrnamePwd :: Handler HaskellCalendar HaskellCalendar()
getUserByUsrnamePwd = do
username <- getPostParam "username"
password <- getPostParam "password"
user <- query_ "SELECT * FROM users WHERE username = ? AND password = ?" (username, password)
liftIO $ print (user :: [User])
我得到一个错误
Expected type: (Maybe ByteString, Maybe ByteString)
-> Handler HaskellCalendar HaskellCalendar [User]
Actual type: (Maybe ByteString, Maybe ByteString) -> [r0]
我真的不知道为什么,因为根据API应该是(也许字节串,也许字节字符串),而不是(也许字节串,也许字节字符串) - > [R0]
此致
谢谢。我也意识到了这一点。干杯! –