[Haskell-beginners] Yesod question - ajax.lhs

Fri May 20 05:47:43 CEST 2011

Michael,
            Your examples have a lot to do with why I picked Yesod in
the first place. I've used a few of them to play around with and get a
better grasp of your framework. I'm not knowledgeable enough at this
point to extrapolate what's wrong with your code and then fix it.
Could you provide a fixed version? I will then use it to play around
with jQuery and see if I can't get a tabbed navbar going. The ultimate
goal is to steal as much as I can from the haskellers design.

Thanks :)

Michael

On Thu, May 19, 2011 at 8:38 PM, Michael Snoyman <michael at snoyman.com> wrote:
> On Fri, May 20, 2011 at 3:38 AM, Michael Litchard <michael at schmong.org> wrote:
>> I'm using yesod 0.8.1
>>
>> I'm playing around with yesod examples 0.8.0.1 and I noticed a few
>> things that send up some red flags
>>
>> first thing, when I try to run ajax.lhs from the top level directory
>>
>>
>>
>>
>> src/ajax.lhs:6:3:
>>    Warning: In the use of `string'
>>             (imported from Yesod, but defined in Text.Blaze.Internal):
>>             Deprecated: "Use Blaze.Html.toHtml"
>
> This is just using an older version of blaze-html. Replacing "string"
> with "toHtml" should work just fine.
>
>> src/ajax.lhs:37:18:
>>    Warning: Deprecated syntax:
>>               quasiquotes no longer need a dollar sign: $parseRoutes
>>
>> src/ajax.lhs:52:21:
>>    Warning: Deprecated syntax:
>>               quasiquotes no longer need a dollar sign: $hamlet
>>
>> src/ajax.lhs:93:17:
>>    Warning: Deprecated syntax:
>>               quasiquotes no longer need a dollar sign: $hamlet
>
> This is intentional. GHC 7 changed the syntax for QQ. The examples
> still mostly use the GHC 6.12 syntax for backwards compatibility.
>
>>
>> This is suggesting to me the example code hasn't caught up to the
>> changes in yesod, which can cause confusion for n00bs like me.
>>
>> I'm trying to learn how to use jQuery via yesod, and when I see the
>> html generated from the current ajax.lhs this is what comes up
>>
>> <!DOCTYPE html><html><head><title>Page 1</title><link rel="stylesheet"
>> href="/static/style%2Ecss?YaQxW21D"><script
>> src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script><script
>> src="/static/script%2Ejs?NWBIzSLG"></script></head><body><ul
>> id="navbar"><li><a href="/page/page%2D1">Page 1</a></li><li><a
>> href="/page/page%2D2">Page 2</a></li><li><a href="/page/page%2D3">Page
>> 3</a></li></ul><div id="content"><h1>Page 1</h1><article>My first
>> page</article></div></body></html>
>>
>> I want to draw attention to
>> <script src="/static/script%2Ejs?NWBIzSLG"> and things like this. This
>> is the other red flag that the example code hasn't caught up to the
>> current state of Yesod. Am I interpreting the problem correctly?
>
> Yesod provides the query string as an optimization to allow you to set
> cache headers. There's a good reason the code looks like that. (Though
> I'm surprised the period is getting URL-encoded, looks like an issue
> with http-types. And before anyone bugs the author of the package, it
> looks like an issue with the code *I* wrote.)
>
>> Here is what the latest example of ajax.lhs looks like. Could someone
>> tell me what needs to change to prevent the above problems from
>> happening?
>>
>>> {-# LANGUAGE TypeFamilies, QuasiQuotes, TemplateHaskell, MultiParamTypeClasses, OverloadedStrings #-}
>>> import Yesod
>>> import Yesod.Helpers.Static
>>> import Data.Monoid (mempty)
>>
>> Like the blog example, we'll define some data first.
>>
>>> data Page = Page
>>>   { pageName :: String
>>>   , pageSlug :: String
>>>   , pageContent :: String
>>>   }
>>
>>> loadPages :: IO [Page]
>>> loadPages = return
>>>   [ Page "Page 1" "page-1" "My first page"
>>>   , Page "Page 2" "page-2" "My second page"
>>>   , Page "Page 3" "page-3" "My third page"
>>>   ]
>>
>>> data Ajax = Ajax
>>>   { ajaxPages :: [Page]
>>>   , ajaxStatic :: Static
>>>   }
>>> type Handler = GHandler Ajax Ajax
>>
>>
>>> staticFiles "static/yesod/ajax"
>>
>>> mkYesod "Ajax" [$parseRoutes|
>>> /                  HomeR   GET
>>> /page/#String      PageR   GET
>>> /static            StaticR Static ajaxStatic
>>> |]
>>
>>
>>> instance Yesod Ajax where
>>>   approot _ = ""
>>>   defaultLayout widget = do
>>>   Ajax pages _ <- getYesod
>>>   content <- widgetToPageContent widget
>>>   hamletToRepHtml [$hamlet|
>>> \<!DOCTYPE html>
>>>
>>> <html>
>>>   <head>
>>>     <title>#{pageTitle content}
>>>     <link rel="stylesheet" href="@{StaticR style_css}">
>>>     <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js">
>>>     <script src="@{StaticR script_js}">
>>>     \^{pageHead content}
>>>   <body>
>>>     <ul id="navbar">
>>>       $forall page <- pages
>>>         <li>
>>>           <a href="@{PageR (pageSlug page)}">#{pageName page}
>>>     <div id="content">
>>>       \^{pageBody content}
>>> |]
>>
>>
>>> getHomeR :: Handler ()
>>> getHomeR = do
>>>   Ajax pages _ <- getYesod
>>>   let first = head pages
>>>   redirect RedirectTemporary $ PageR $ pageSlug first
>>
>>> getPageR :: String -> Handler RepHtmlJson
>>> getPageR slug = do
>>>   Ajax pages _ <- getYesod
>>>   case filter (\e -> pageSlug e == slug) pages of
>>>       [] -> notFound
>>>       page:_ -> defaultLayoutJson (do
>>>           setTitle $ string $ pageName page
>>>           addHamlet $ html page
>>>           ) (json page)
>>>  where
>>>   html page = [$hamlet|
>>> <h1>#{pageName page}
>>> <article>#{pageContent page}
>>> |]
>>>   json page = jsonMap
>>>       [ ("name", jsonScalar $ pageName page)
>>>       , ("content", jsonScalar $ pageContent page)
>>>       ]
>>
>>> main :: IO ()
>>> main = do
>>>   pages <- loadPages
>>>   let s = static "static/yesod/ajax"
>>>   warpDebug 3000 $ Ajax pages s
>>
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