如何在 Yesod-Persistent 中使用记录语法

Question

为什么以下操作不起作用？我有点知道引擎盖下有很多东西，User 类型可能实际上没有email、createdAt 和updatedAt 字段。不使用容易失控的位置参数实例化对象的最佳方法是什么？

share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
User
  email String
  createdAt UTCTime Maybe default=CURRENT_TIME
  updatedAt UTCTime Maybe default=CURRENT_TIME
  deriving Show
]]

main :: IO ()
main = runSqlite ":memory:" $ do
  runMigration migrateAll
  u <- insert $ User {email="saurabhnanda@gmail.com" createdAt=Nothing updatedAt=Nothing}

编译错误：

trysql.hs:38:23:
    ‘email’ is not a (visible) field of constructor ‘User’

trysql.hs:38:55:
    ‘createdAt’ is not a (visible) field of constructor ‘User’

trysql.hs:38:74:
    ‘updatedAt’ is not a (visible) field of constructor ‘User’

Answer 1

函数名称类似于：userEmail、userCreatedAt、userUpdatedAt。

运行 cabal REPL 并浏览项目有助于识别 Yesod 为持久类型生成的函数。