description

# CreateTimerHandler typedef

CreateTimerHandler = Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration duration, void f())

The type of a custom Zone.createTimer implementation function.

A function used as ZoneSpecification.createTimer to specialize the behavior of a new zone.

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 callback function `f` and `duration` are the ones which were passed to Zone.createTimer of `zone` (possibly through the Timer constructor).

The custom handler can choose to replace the function `f` with one that does something before, after or instead of calling `f`, and then call `parent.createTimer(zone, replacement)`. or it can implement its own timer queue, which typically still depends on `parent.createTimer` to as a way to get started.

The function should return a Timer object which can be used to inspect and control the scheduled timer callback.

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 CreateTimerHandler = Timer Function(
      Zone self,
      ZoneDelegate parent,
      Zone zone,
      Duration duration,
      void Function() f,
    );