SignalUpdater<V> typedef Null safety

SignalUpdater<V> = V Function(V initialValue, V preValue, Signal signal)

Updates a value when a signal occurs.

The initialValue is the value set in the specification. The preValue is previous value before this update.

Make sure the return value is a different instance from initialValue or preValue.


typedef SignalUpdater<V> = V Function(
    V initialValue, V preValue, Signal signal);