Managing screens.
WHAT A VIEW CONTROLLER IS
An object managing a screen or portion of one, with its own lifecycle.
WHAT THE LIFECYCLE INVOLVES
Loading, appearing, appeared, disappearing, disappeared.
WHAT TO DO IN EACH
Set up once on load Update state before appearing Start work when appeared Stop work when disappearing
WHY THAT LAST POINT
Work continuing on a hidden screen wastes battery and may crash on a deallocated view.
WHAT CONTAINER CONTROLLERS DO
Manage other controllers: navigation stacks, tab bars, split views.
WHAT A NAVIGATION STACK PROVIDES
Pushing and popping screens, with a back control.
WHAT TO ENSURE
That the navigation makes sense from any entry point, including a notification or a link.
WHAT MODAL PRESENTATION IS FOR
A task requiring completion or dismissal before continuing.
WHAT TO AVOID
Stacking modals Modals where a pushed screen would serve
WHAT TO HANDLE
The gesture that dismisses a modal, which users may perform mid-task.
WHAT TO DO ABOUT UNSAVED WORK
Confirm before discarding.
