description

# RunUnaryHandler typedef

RunUnaryHandler = R Function<R, T>(Zone self, ZoneDelegate parent, Zone zone, R f(T arg), T arg)

The type of a custom Zone.runUnary implementation function.

A function used as ZoneSpecification.runUnary 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 function `f` and value `arg` are the function and argument which was passed to the Zone.runUnary of `zone`.

The default behavior of Zone.runUnary is to call `f` with argument `arg` 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 RunUnaryHandler =
        R Function<R, T>(
          Zone self,
          ZoneDelegate parent,
          Zone zone,
          R Function(T arg) f,
          T arg,
        );