RunHandler typedef Null safety

R RunHandler<R>(
  1. Zone self,
  2. ZoneDelegate parent,
  3. Zone zone,
  4. R f(
      )
    )

    The type of a custom Zone.run implementation function.

    Receives the Zone that the handler was registered on as self, a delegate forwarding to the handlers of self's parent zone as parent, and the current zone where the error was uncaught as zone, which will have self as a parent zone.

    The function f is the function which was passed to the Zone.run of zone.

    The default behavior of Zone.run is to call f in the current zone, zone. A custom handler can do things before, after or instead of calling f.

    The function must only access zone-related functionality through self, parent or zone. It should not depend on the current zone (Zone.current).

    Implementation

    typedef RunHandler = R Function<R>(
    Zone self, ZoneDelegate parent, Zone zone, R Function() f);