[web-devel] [Yesod] Creating a static link

Michael Snoyman michael at snoyman.com
Sun Feb 13 05:40:21 CET 2011

On Sat, Feb 12, 2011 at 11:59 PM, Rafael Cunha de Almeida
<rafael-lists at kontesti.me> wrote:
> Hello,
> From what I could gather, the way to create a link to a static page,
> like a picture is:
>        StaticR $ StaticRoute ["figure.png"] []
> I wanted to add a static picture in my site's template so I added
>        <img alt="" src=@{StaticR $ StaticRoute ["figure.png"] []}>
> to my template. Unfortunately, that didn't work. It seems like creating
> lists inside @{} or even #{} is impossible. For instance
>        #{head ["test"]}
> doesn't work either.
> Is that a bug? Or is it how it's supposed to work?

You could go either way on that one. The content of an interpolation
is specifically *not* a fully-powered Haskell expression. The question
is what syntax do we want to include. I had not thought of including
list notation, and I don't see any technical barrier to adding it. As
with most template systems, Hamlet needs to strike a balance between
power and simplicity: I could go either way on this specific one.

However, for your use case, I would recommend a different approach:
Yesod.Helpers.Static provides a Template Haskell function calls
staticFiles. If you include it at the top level of your code like

    staticFile "static"

It will create an identifier for each and every file in your static
folder. In that case, you could replace your Hamlet code with:

        <img alt="" src=@{StaticR figure_png}>

I'm open to discussion regarding adding list notation to interpolations.


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