这是我的项目(原始资料来自FP Haskell中心,但我不知道如何公开提供它)https://github.com/geraldus/EsqueletoTest
有YesodPersist实例声明
instance YesodPersist App where
type YesodPersistBackend App = SqlBackend -- line 19
runDB action = do
App pool <- getYesod
runSqlPool action pool
我有以下错误:
src/Foundation.hs@19:36-19:46 Kind mis-match
Expected kind `(* -> *) -> * -> *', but SqlBackend has kind * …
In the type `SqlBackend'
In the type synonym instance declaration for `YesodPersistBackend'
In the instance declaration for `YesodPersist App'
出了什么问题?
答案 0 :(得分:1)
看起来您最初使用Persistent 2编写代码,现在使用Persistent 1.3。在1.3上,你需要像type YesodPersistBackend App = SqlPersistT
这样的东西。