Advanced: optimistic UI updates (and UNDO action)

[w3b3]

It is a pain to wait for 2 API calls to fully resolve to ONLY THEN be able to continue operating with the App.

It feels weird. It should be instantaneous. API responses should come whenever AND (ONLY THEN) we will worry with a error state.

Examples:

• I will send a delete entry call
  • The app should assume the call was successfully submitted and responded at the same instance. Meaning the task should be removed from the screen upon clicking.
  • When the API returns a 200, the list is updated (maybe a new pagination, maybe a new ordering) but the user is already interacting with something else.
  • When the API returns a 400/500 response, a pop-up is displayed to the user and the response comes back with a revert operation in whatever was changed (maybe the old state of the article list has to be promoted again, since the fast one is not the most accurate given the bad response).

This implies that some actions will have to cache/keep an old state and a new state in memory. The new state always replaces instantaneously and the old state is only used when the response is bad. If response is good, old state is discarded.