RunHandler typedef Null safety

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