Zone class - dart:async library (original) (raw)
A zone represents an environment that remains stable across asynchronous calls.
All code is executed in the context of a zone, available to the code as Zone.current. The initial main function runs in the context of the default zone (Zone.root). Code can be run in a different zone using eitherrunZoned or runZonedGuarded to create a new zone and run code in it, or Zone.run to run code in the context of an existing zone which may have been created earlier using Zone.fork.
Developers can create a new zone that overrides some of the functionality of an existing zone. For example, custom zones can replace or modify the behavior of print, timers, microtasks or how uncaught errors are handled.
The Zone class is not subclassable, but users can provide custom zones by forking an existing zone (usually Zone.current) with a ZoneSpecification. This is similar to creating a new class that extends the base Zone class and that overrides some methods, except without actually creating a new class. Instead the overriding methods are provided as functions that explicitly take the equivalent of their own class, the "super" class and thethis object as parameters.
Asynchronous callbacks always run in the context of the zone where they were scheduled. This is implemented using two steps:
- the callback is first registered using one of registerCallback,registerUnaryCallback, or registerBinaryCallback. This allows the zone to record that a callback exists and potentially modify it (by returning a different callback). The code doing the registration (e.g.,
Future.then) also remembers the current zone so that it can later run the callback in that zone. - At a later point the registered callback is run in the remembered zone, using one of run, runUnary or runBinary.
This is all handled internally by the platform code and most users don't need to worry about it. However, developers of new asynchronous operations, provided by the underlying system, must follow the protocol to be zone compatible.
For convenience, zones provide bindCallback (and the correspondingbindUnaryCallback and bindBinaryCallback) to make it easier to respect the zone contract: these functions first invoke the corresponding registerfunctions and then wrap the returned function so that it runs in the current zone when it is later asynchronously invoked.
Similarly, zones provide bindCallbackGuarded (and the correspondingbindUnaryCallbackGuarded and bindBinaryCallbackGuarded), when the callback should be invoked through Zone.runGuarded.
Annotations
- @vmIsolateUnsendable
Properties
The error zone is responsible for dealing with uncaught errors.
no setter
The hash code for this object.
no setterinherited
The parent zone of the this zone.
no setter
A representation of the runtime type of the object.
no setterinherited
Methods
bindBinaryCallback<R, T1, T2>(R callback(T1 argument1, T2 argument2))→ ZoneBinaryCallback<R, T1, T2>
Registers the provided callback and returns a function that will execute in this zone.
bindBinaryCallbackGuarded<T1, T2>(void callback(T1 argument1, T2 argument2))→ void Function(T1, T2)
Registers the provided callback and returns a function that will execute in this zone.
bindCallback<R>(R callback())→ ZoneCallback<R>
Registers the provided callback and returns a function that will execute in this zone.
bindCallbackGuarded(void callback())→ void Function()
Registers the provided callback and returns a function that will execute in this zone.
bindUnaryCallback<R, T>(R callback(T argument))→ ZoneUnaryCallback<R, T>
Registers the provided callback and returns a function that will execute in this zone.
bindUnaryCallbackGuarded<T>(void callback(T argument))→ void Function(T)
Registers the provided callback and returns a function that will execute in this zone.
createPeriodicTimer(Duration period, void callback(Timer timer))→ Timer
Creates a periodic Timer where the callback is executed in this zone.
createTimer(Duration duration, void callback())→ Timer
Creates a Timer where the callback is executed in this zone.
errorCallback(Object error, StackTrace? stackTrace)→ AsyncError?
Intercepts errors when added programmatically to a Future or Stream.
fork({ZoneSpecification? specification, Map<Object?, Object?>? zoneValues})→ Zone
Creates a new zone as a child zone of this zone.
handleUncaughtError(Object error, StackTrace stackTrace)→ void
Handles uncaught asynchronous errors.
inSameErrorZone(Zone otherZone)→ bool
Whether this zone and otherZone are in the same error zone.
noSuchMethod(Invocation invocation)→ dynamic
Invoked when a nonexistent method or property is accessed.
inherited
Prints the given line.
registerBinaryCallback<R, T1, T2>(R callback(T1 arg1, T2 arg2))→ ZoneBinaryCallback<R, T1, T2>
Registers the given callback in this zone.
registerCallback<R>(R callback())→ ZoneCallback<R>
Registers the given callback in this zone.
registerUnaryCallback<R, T>(R callback(T arg))→ ZoneUnaryCallback<R, T>
Registers the given callback in this zone.
run<R>(R action())→ R
Executes action in this zone.
runBinary<R, T1, T2>(R action(T1 argument1, T2 argument2), T1 argument1, T2 argument2)→ R
Executes the given action with argument1 and argument2 in this zone.
runBinaryGuarded<T1, T2>(void action(T1 argument1, T2 argument2), T1 argument1, T2 argument2)→ void
Executes the given action with argument1 and argument2 in this zone and catches synchronous errors.
runGuarded(void action())→ void
Executes the given action in this zone and catches synchronous errors.
runUnary<R, T>(R action(T argument), T argument)→ R
Executes the given action with argument in this zone.
runUnaryGuarded<T>(void action(T argument), T argument)→ void
Executes the given action with argument in this zone and catches synchronous errors.
scheduleMicrotask(void callback())→ void
Runs callback asynchronously in this zone.
A string representation of this object.
inherited
Operators
operator ==(Object other)→ bool
The equality operator.
inherited
operator [](Object? key)→ dynamic
Retrieves the zone-value associated with key.
Static Properties
The zone that is currently active.
no setter
Constants
The root zone.