CODEWITHSUNDEEP
haskellyesod
user2986209
user2986209

Reputation: 15

Get a session value with lookupSession

I try to put a session value in a variable to display it in my .hamlet but it does not focntion!

 getEtatR :: Handler Html
 getEtatR = do
     mSessionValue <- lookupSession "myKey"
     let myValue = mSessionValue :: Maybe Text
     defaultLayout $ do
         aDomId <- newIdent
         setTitle "mon titre"
         $(widgetFile "etatWidget")

I need #{myValue} to put it in my etat.hamlet

Upvotes: 1

Views: 151

Answers (2)

jamshidh
jamshidh

Reputation: 12070

The problem is the type of myValue, which is Maybe Text. In order for a variable to show up in the template, it has to be an instance of Text.Blaze.ToMarkup.... So Text, String, or Int would all work, but "Maybe a" does not.

There are many ways to convert a "Maybe Text" to a ToMarkup. If you know for sure that the Maybe will not be a "Nothing", just strip the maybe using fromJust (imported from Data.Maybe).... But beware that if it ever does come up as a Nothing the program will crash. Similarly you could use a case statement to fill in the Nothing case, like this

myVariable = case mSessionValue of
                         Just x -> x
                         Nothing -> "<No session value>"

You can also do a quick check by converting mSessionValue to a string using show.

The following works for me....

getEtatR :: Handler Html
getEtatR = do
     mSessionValue <- lookupSession "myKey"
     let myValue = show mSessionValue
     defaultLayout $ do
         aDomId <- newIdent
         setTitle "mon titre"
         $(widgetFile "etatWidget")

using etatWidget.hamlet

<h1>#{myValue}

Upvotes: 1

Ecognium
Ecognium

Reputation: 2076

If all you want is to display the value and get it out of Maybe, you can do this directly inside the hamlet

$maybe val <- mSessionValue
   <p>#{val}
$nothing
    <p>No Value Set

Upvotes: 0

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