Question

我正在尝试设置硬编码的身份验证，以依赖Yesod脚手架中config/settings.yml中指定的登录信息。我写了以下代码：

instance YesodAuthHardcoded App where
    validatePassword u = do
        app <- getYesod
        let user = appUser $ appSettings app
        return . validPassword user u . fromString . unpack
    doesUserNameExist = do
        app <- getYesod
        return . isJust . lookupUser app

我收到validatePassord的以下错误消息以及doesUserNameExist的等效消息：

• Couldn't match type ‘HandlerSite ((->) Text)’ with ‘App’
  Expected type: Text -> App
    Actual type: Text -> HandlerSite ((->) Text)
• In a stmt of a 'do' block: app <- getYesod
  In the expression:
    do { app <- getYesod;
         let user = appUser $ appSettings app;
         return . validPassword user u . fromString . unpack }
  In an equation for ‘validatePassword’:
      validatePassword u
        = do { app <- getYesod;
               let user = ...;
               return . validPassword user u . fromString . unpack }

validatePassword is defined in Yesod.Auth.Hardcoded的原型：

validatePassword :: Text -> Text -> AuthHandler site Bool

和AuthHandler is defined in Yesod.Auth：

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

最后getYesod is defined as follow in Yesod.Core.Handler：

getYesod :: MonadHandler m => m (HandlerSite m)

从这些定义看来，我应该有办法从getYesod monad调用AuthHandler，但我无法弄清楚如何。

编辑：我已将yesod及其脚手架更新为最新版本。我还修改了validatePassword如下：

validatePassword u = do
    app <- liftHandler . getYesod
    let user = appUser $ appSettings app
    return . validPassword user u . fromString . unpack

我收到以下错误消息：

    • Couldn't match type ‘m1 a1’ with ‘App’
      Expected type: HandlerFor (HandlerSite m1) a1 -> App
        Actual type: HandlerFor (HandlerSite m1) a1 -> m1 a1
    • In the first argument of ‘(.)’, namely ‘liftHandler’
      In a stmt of a 'do' block: app <- liftHandler . getYesod
      In the expression:
        do app <- liftHandler . getYesod
           let user = appUser $ appSettings app
           return . validPassword user u . fromString . unpack
    |
259 |         app <- liftHandler . getYesod
    |

Answer 1

该错误来自我尝试修改Yesod.Auth.Hardcoded模块提供的代码段。我引入了一个与省略的参数冲突的do符号。指定参数可以解决问题，代码变为：

instance YesodAuthHardcoded App where
    validatePassword u p = do
        app <- getYesod
        let user = appUser $ appSettings app
        return . validPassword user u . fromString $ unpack p
    doesUserNameExist u = do
        app <- getYesod
        return . isJust $ lookupUser app u

Yesod硬编码身份验证取决于AppSettings

1 个答案: