Data driving the interface.
WHAT STATE IS HERE
Observable values that trigger recomposition when changed.
WHAT REMEMBERING DOES
Retains a value across recompositions.
WHAT IT DOES NOT SURVIVE
Configuration changes, unless the saving variant is used.
WHAT THAT MEANS
Rotation loses it, unless handled.
WHAT STATE HOISTING IS
Moving state up to a caller, so the composable receives the value and reports events.
WHY IT MATTERS
It makes composables reusable, testable and previewable.
WHAT THE PATTERN IS
State flows down; events flow up.
WHAT TO KEEP IN A VIEW MODEL
State surviving configuration changes and belonging to the screen.
WHAT TO KEEP LOCAL
Transient interface state: whether something is expanded, scroll position.
WHAT TO AVOID
Deriving values and storing them, rather than computing during composition Mutating collections in place, which is not observed State duplicated in several places
WHY MUTATION IS NOT OBSERVED
Compose compares references, so a mutated list appears unchanged.
WHAT TO DO INSTEAD
Produce a new value.
