Re: [web-devel] Getting the http request header in Yesod?

On Sun, Sep 26, 2010 at 12:20 PM, Michael Snoyman wrote:

On Sun, Sep 26, 2010 at 10:10 AM, Rehno Lindeque wrote:

...

One more question. Is it possible to manipulate the request header when doing a redirect? For example, at one I have (redirect RedirectTemporary $ AuthR LoginR), but "X-Requested-With" isn't being passed through...

No, the request headers are set by the browser, and you can't directly affect them. What you *could* do is set a session variable or something. However, your best bet is probably to redirect to a URL with a query-string parameter indicated the request-with information and then check both the request header and the query string parameter.

Michael

Thought I'd mention that this worked out very nicely in Yesod. I modified the default layout to return only the page contents of a request if it is an ajax request, but add all the surrounding html if it isn't. I also used a session variable for the redirected ajax requests. At first I just wanted to call the correct handler directly instead of redirecting if it was a ajax request but since getLoginR is private to Yesod.Helpers.Auth I had to redirect and the session variable was actually very simple to set and check. I.e. If anyone is curious it looks like this:

isAjaxRequest :: GHandler master sub Bool isAjaxRequest = do   request    <- waiRequest   sessionVar <- lookupSession Session.ajaxRequestKey   return $     (isJust $       listToMaybe $         filter (\(k,v) -> k == mkCIByteString "X-Requested-With" && B8.map toLower v == "xmlhttprequest") $           requestHeaders request)     || isJust sessionVar

instance Yesod  where     defaultLayout widget = do         mmsg  <-  getMessage         mAuth <-  maybeAuth

-- Get the page contents         pc    <- widgetToPageContent $ do             widget             addStyle $(Settings.cassiusFile "default-layout")

        -- Check whether this is a ajax request         isAjax <-  isAjaxRequest         deleteSession Session.ajaxRequestKey

-- Return either the page body if it's an ajax request or embed in the default layout if it's a normal request         hamletToRepHtml $           if isAjax then pageBody pc           else $(Settings.hamletFile "default-layout")

Of course when you redirect you have to set the session variable like this:

  isAjax <- isAjaxRequest   if isAjax then setSession Session.ajaxRequestKey "true" else return ()   redirect RedirectTemporary $ AuthR LoginR

Rehno