[Haskell-cafe] Ensuring that blank-state has been handled in UIs?
tomas.carnecky at gmail.com
Sun Apr 16 12:03:26 UTC 2017
Make your 'displayTable' function take a 'NonEmpty a' instead of a List
(eg. [a] or Vector a). That at least ensures that you won't ever be showing
an empty table. I don't think there is a Map/Set-equivalent of NonEmpty.
But you will have to convert a Map/Set into a list at some point, and
that's where you can again use NonEmpty.
On Sun, Apr 16, 2017 at 1:54 PM Saurabh Nanda <saurabhnanda at gmail.com>
> Hi Everyone,
> In most user-interfaces we need special-treatment for blank states
> (zero-item state). For example:
> * In case there are no customers, don't show an empty table, instead show
> the message "You seem to have no customers, why not start by creating
> * In case there are no bookings, don't show an empty table, instead show
> the message, "No bookings here. Want to create one?"
> * In case there are no search results, don't show an empty table, instead
> show the message, "No items found. Undo your last filter?"
> In some cases, the one-item case also needs special treatment, but I'm
> unable to come with relatable examples at the moment.
> A lot of times the dev simply forgets about the blank state, and it is
> caught during QA, which results in a quick-fix on the following lines:
> if length item > 0 then displayTable else showBlankState
> if Data.Map.Strict.size map > 0 then displayTable else showBlankState
> if Data.Set.Ordered.size set > 0 then displayTable else showBlankState
> Is there a way to prevent this bug from the get-go? Can we use the
> type-system (or anything else) to enforce the dev to at least _think_ about
> the blank state? Obviously, the type system can't help us with _what_ needs
> to be done with the blank state, but at least it can _remind_ the dev at
> compile-time about handling blank states.
> -- Saurabh.
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