Question

我正在尝试添加

instance YesodAuthEmail App

到Yesod-Postgres脚手架（yesod版本1.6）并且遇到编译错误。

相关代码是：

instance YesodAuth App where
     type AuthId App = UserId
     ....
     authPlugins :: App -> [AuthPlugin App]
     authPlugins app = [authOpenId Claimed []] ++ extraAuthPlugins
         where extraAuthPlugins = [ authEmail ]

instance YesodAuthEmail App where
    type AuthEmailId App = UserId

    afterPasswordRoute _ = HomeR

    addUnverified email verkey =
        runDB $ insert $ User email Nothing

我收到的错误是：

/home/justin/code/yesodemail/src/Foundation.hs:273:11: error: • Could not deduce: m ~ HandlerFor site0 from the context: MonadAuthHandler App m bound by the type signature for: addUnverified :: Yesod.Auth.Email.Email -> VerKey -> AuthHandler App (AuthEmailId App) .... Expected type: m (AuthEmailId App) Actual type: HandlerFor site0 (Key User)

根据类型，

getEmail :: AuthEmailId site -> AuthHandler site (Maybe Email) 
type MonadAuthHandler master m = (MonadHandler m, YesodAuth master, master ~ HandlerSite m, Auth ~ SubHandlerSite m, MonadUnliftIO m)
type AuthHandler master a = forall m. MonadAuthHandler master m => m a

我原本以为这会编译。我误解了什么？

P.S。我试图包含所有相关内容，但完整的Foundation.hs位于https://gist.github.com/hyperpape/39d4d2baf67d3bdbdba45a943e7e0425

Answer 1

runDB的类型是：

runDB :: YesodDB site a -> HandlerFor site a

要在AuthHandler中调用它，您需要将其提升到HandlerFor。

如果我没有记错，这就是MonadHandler runDB方法的用途。

如果您使用它撰写addUnverified email verkey = liftHandler . runDB $ insert $ User email Nothing来电，则应该有效：

{
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Data / Import",
            "type": "process",
            "command": "php",
            "args": [
                "data/bin/import.php"
            ]
        }
    ]
}

我找到了问题liftHandler的详细答案。

YesodAuthEmail无法推断m~HandlerFor site0

1 个答案: