Getting an XHR Going

[Lally Singh]

I'm trying to have a <div> show the results of an XHR (that returns JSON from a yesod app).

But, I can't seem to figure out how to effectively create an Event t XhrRequest.  I can create an XhrRequest, but that's about it.  I tried updated $ constDyn $ xhrRequest "GET" url def, which compiled, but didn't actually do the request.  I feel that I'm missing something quite fundamental here.  Is there another event, like onLoad, that I should piggyback into for creating the XhrRequest?

Thanks in advance!

[Sean Leather]

Hi Lally,

On Tue, Mar 8, 2016 at 4:50 PM, Lally Singh wrote:

I'm trying to have a <div> show the results of an XHR (that returns JSON from a yesod app).

But, I can't seem to figure out how to effectively create an Event t XhrRequest.  I can create an XhrRequest, but that's about it.  I tried updated $ constDyn $ xhrRequest "GET" url def, which compiled, but didn't actually do the request.  I feel that I'm missing something quite fundamental here.  Is there another event, like onLoad, that I should piggyback into for creating the XhrRequest?

Does newEventWithTriggerRef help you? You can then trigger an event with an IO function.

Personally, I prefer this simplifying wrapper:

newEventAndTrigger :: MonadWidget t m => m (Event t a, a -> IO ())

newEventAndTrigger = do

  postGui <- askPostGui

  runWithActions <- askRunWithActions

  (e, triggerRef) <- newEventWithTriggerRef

  return (e, \a ->

    readRef triggerRef >>=

    maybe (return ()) (\t -> postGui $ runWithActions [t :=> a]))

Regards,

Sean

[Lally Singh]

Sean, thank you.

I started at newEventAndTrigger and kept digging a bit.  I found getPostBuild, which seemed to do the trick.  Is that reasonable, or is it only working because of bad luck? 

[Sean Leather]

Perfectly reasonable! Now I understand what you meant by onLoad. I was thinking of the XHR onload(), but you meant the point at which the DOM was loaded/ready. That's exactly what getPostBuild is intended for.

Regards,

Sean