Re: [web-devel] Monad transformers with Warp/WAI

On Sat, May 16, 2015 at 10:05 PM Alex wrote:

On Sat, 16 May 2015 18:30:31 +0000 Michael Snoyman wrote:

...

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.

Is a consequence of this design that I have to use runReaderT every time I want to use a function of the type (Foo -> MyApp Bar) from within myApp? Is it better/easier to simply rewrite the all functions myApp calls so that they accept an AppConfig parameter instead of returning a MyApp Bar?

-- Alex

That's one approach. You can also do something like: myApp appConfig req respond = flip runReaderT appConfig $ do someFunc ... someFunc :: MyApp ()