[Haskell-cafe] writing wizards in Yesod

[Henning Thielemann]

On Wed, 26 Aug 2020, Olaf Klinke wrote:

> The Yesod book [1,2] gives examples where state is encoded in an IORef
> inside the foundational type, like so: 
>
>   data AppState = ...
>   data App = App {appState :: IORef AppState}

IORef sounds mighty wrong, because a web server is highly concurrent.