This example shows a UI for searching books. It uses an https endpoint provided by Internet Archive's Open Library, which allows querying books using any piece of information (title, authors, ISBN, etc).
The BookTypes module defines, besides all the needed types, the Aeson instances used to deserialize the JSON response returned by the API. Only a few fields are retrieved and displayed in the UI, but quite a few more are available.
The BooksSearch event is used to run a Task that calls the https endpoint.
When a successful response is received, an event with the result is sent back to
the application. The same happens with errors, which are displayed as an alert
dialog. Note: In case you use wreq for your own projects, it is recommended
that you use Session; without it, memory consumption increases heavily.
The zstack widget is used to always keep the background visible while showing details or errors. Unless specifically requested, input is only received by the top layer of zstack.
A box with the mergeRequired configuration option set is used to avoid
running the merge process on the result widgets whenever the model changes. This
happens when the user inputs text, a dialog is displayed and other scenarios.
This is an optimization and should not be needed unless performance is a concern
(for example, when a long list of items is displayed).
booksChanged wenv old new = old ^. books /= new ^. books
box_ [mergeRequired booksChanged] $
vscroll (vstack (bookRow wenv <$> model ^. books)) `nodeKey` "mainScroll"