Question

I dont seem to be able to understand how to get the form data with heist.
I just started looking into Haskell web frameworks but documentation is a bit … scarce, to say the least. There is no mention of forms in the skinny heist tutorial on the snap website.
So given a simple html form, how do I get the form data for processing into my handler function? Can anyone point me to a tutorial, google just keeps quiet on this one? Or maybe a short example …

Also, where do I get information on the conditional control? Say, if I want conditionally include certain parts of the html within my page, how do I do it with heist? Basically, where is the “if”?

Thanks

Answer 1

See Using digestive functors with Heist for a good tutorial on simple forms, and mightybyte’s musings about heist. If you’re planning on using multipart/form-data use the Snap.Util.FileUploads module.

You could use a Splice to generate content based on a condition.
A Splice returns a list of Node‘s,

mySplice = do
  -- get environment conditions
  -- condition could be passed in as a parameter 
  if condition 
     then return [] -- do nothing
     else return [TextNode "some content"] -- see Text.XmlHtml

You would then bind this splice to a tag using something like:

bindSplice myTag mysplice defaultHeistState

And place <myTag/> in your template. When Heist renders the template, it will evaluate the splice when it encounters the tag and insert the value in its place.