[web-devel] Monad transformers with Warp/WAI

[Michael Snoyman]

Typically it would look something like this:

myApp :: AppConfig -> Application

main = do
  appConfig <- getAppConfig
  run 3000 $ myApp appConfig

Within myApp, you can now access the AppConfig value and use runReaderT to
unwrap your MyApp transformer.

On Sat, May 16, 2015 at 3:03 PM Alex <alex323 at gmail.com> wrote:

> Hello:
>
> I am writing a small application which receives HTTP requests,
> translates them to JSON, and queues the requests using RabbitMQ.
>
> I created a Monad transformer stack (ReaderT AppConfig IO a) to carry
> around my application configuration and AMQP connection handle (MVar
> Connection within AppConfig), but I am having difficulty determining how
> to integrate it with my Warp application.
>
> The function which is responsible for accepting Requests and returning
> Responses (app :: Application) needs to call functions which require
> AppConfig. For example: (sendToRabbitMQ :: RPCRequest -> MyApp
> ByteString) is a blocking call which requires the AMQP connection
> handle found within AppConfig, which is why it returns a MyApp
> ByteString as opposed to a IO ByteString. If I want to call
> `sendToRabbitMQ' from `app', then the type of `app' needs to change
> from Application to something else, but I am not sure what that should
> be.
>
> What's the best way to proceed?
>
> --
> Alex
> _______________________________________________
> web-devel mailing list
> web-devel at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/web-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/web-devel/attachments/20150516/6041fb1e/attachment.html>