An abstract trait unifying invariant and mutating targets. This object is responsible
for keeping track of the dependents of an event source which is defined as the outer
object, sharing the same id as its targets. As a Reactor, it has a method to
propagate a fired event.
An abstract trait unifying invariant and mutating targets. This object is responsible for keeping track of the dependents of an event source which is defined as the outer object, sharing the same
idas its targets. As aReactor, it has a method topropagatea fired event.