如何从(Yesod/Haskell Project [英] How get the user ID from the Session at (Yesod / Haskell Project

问题描述

伙计，我有一个项目，我需要从会话中引出该用户的ID.

guys i got a little projet and i need to extrat de ID of the user from the Session.

我不能将其放在Text/Int中，因为它说会话带有密钥(我认为是Sql Key)，我如何将其转换为Int以在项目中的其他方法中使用

I can't put it in a Text/Int because it says that the Session carry an Key (Sql Key i think) how can i converte it to Int to use in other methods from my project

我试图这样做是为了从会话中恢复ID

I Tried to do it to recover the ID from session

getInicioR :: Handler Html
getInicioR = do
        uid <- lookupSession "_ID"
        user <- runDB $ get404 uid 

显示以下错误消息:

Couldn't match expected type ‘Key t0’ with actual type ‘Maybe Text’
In the first argument of ‘get404’, namely ‘uid’
In the second argument of ‘($)’, namely ‘get404 uid’

推荐答案

使用 keyToValues 获取

Use keyToValues to get a list of PersistValue values.

keyToValues :: Key record -> [PersistValue]

例如，如果您知道键是一个Text值，那么您的列表将包含一个 PersistText 值，您可以这样进行:

If you know, for instance, that the key is a Text value, then your list will consist of a single PersistText value and you could proceed like this:

do uid <- lookupSession "_ID"
   let pvals = keyToValues uid
       [ PersistText txt ] = pvals
   liftIO $ print pvals            -- to see what pvals is
   -- now txt is a Text value
   ...

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