ZoneSpecification abstract final

abstract final class ZoneSpecification

A parameter object with custom zone function handlers for Zone.fork.

A zone specification is a parameter object passed to Zone.fork and any underlying ForkHandler custom implementations. The individual handlers, if set to a non-null value, will be the implementation of the corresponding Zone methods for a forked zone created using this zone specification.

Handlers have the same signature as the same-named methods on Zone, but receive three additional arguments:

1. The zone the handlers are attached to (the "self" zone). This is the zone created by Zone.fork where the handler is passed as part of the zone delegation.
2. A ZoneDelegate to the parent zone.
3. The "current" zone at the time the request was made. The self zone is always a parent zone of the current zone.

Handlers can either stop propagating the request (by simply not calling the parent handler), or forward to the parent zone, potentially modifying the arguments on the way.

Constructors

ZoneSpecification() factory const

const factory ZoneSpecification({
  (void Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace stackTrace))? handleUncaughtError,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? run,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f, T arg))? runUnary,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f, T1 arg1, T2 arg2))? runBinary,
  (R Function() Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? registerCallback,
  (R Function(T) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f))? registerUnaryCallback,
  (R Function(T1, T2) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f))? registerBinaryCallback,
  (AsyncError? Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace? stackTrace))? errorCallback,
  (void Function(Zone self, ZoneDelegate parent, Zone zone, void Function() f))? scheduleMicrotask,
  (Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration duration, void Function() f))? createTimer,
  (Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration period, void Function(Timer timer) f))? createPeriodicTimer,
  (void Function(Zone self, ZoneDelegate parent, Zone zone, String line))? print,
  (Zone Function(Zone self, ZoneDelegate parent, Zone zone, ZoneSpecification? specification, Map<Object?, Object?>? zoneValues))? fork,
})

Creates a specification with the provided handlers.

If the handleUncaughtError is provided, the new zone will be a new "error zone" which will prevent errors from flowing into other error zones (see Zone.errorZone, Zone.inSameErrorZone).

Implementation

const factory ZoneSpecification({
  HandleUncaughtErrorHandler? handleUncaughtError,
  RunHandler? run,
  RunUnaryHandler? runUnary,
  RunBinaryHandler? runBinary,
  RegisterCallbackHandler? registerCallback,
  RegisterUnaryCallbackHandler? registerUnaryCallback,
  RegisterBinaryCallbackHandler? registerBinaryCallback,
  ErrorCallbackHandler? errorCallback,
  ScheduleMicrotaskHandler? scheduleMicrotask,
  CreateTimerHandler? createTimer,
  CreatePeriodicTimerHandler? createPeriodicTimer,
  PrintHandler? print,
  ForkHandler? fork,
}) = _ZoneSpecification;

ZoneSpecification.from() factory

factory ZoneSpecification.from(
  ZoneSpecification other, {
  (void Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace stackTrace))? handleUncaughtError,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? run,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f, T arg))? runUnary,
  (R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f, T1 arg1, T2 arg2))? runBinary,
  (R Function() Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? registerCallback,
  (R Function(T) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f))? registerUnaryCallback,
  (R Function(T1, T2) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f))? registerBinaryCallback,
  (AsyncError? Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace? stackTrace))? errorCallback,
  (void Function(Zone self, ZoneDelegate parent, Zone zone, void Function() f))? scheduleMicrotask,
  (Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration duration, void Function() f))? createTimer,
  (Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration period, void Function(Timer timer) f))? createPeriodicTimer,
  (void Function(Zone self, ZoneDelegate parent, Zone zone, String line))? print,
  (Zone Function(Zone self, ZoneDelegate parent, Zone zone, ZoneSpecification? specification, Map<Object?, Object?>? zoneValues))? fork,
})

Creates a specification from other and provided handlers.

The created zone specification has the handlers of other and any individually provided handlers. If a handler is provided both through other and individually, the individually provided handler overrides the one from other.

Implementation

factory ZoneSpecification.from(
  ZoneSpecification other, {
  HandleUncaughtErrorHandler? handleUncaughtError,
  RunHandler? run,
  RunUnaryHandler? runUnary,
  RunBinaryHandler? runBinary,
  RegisterCallbackHandler? registerCallback,
  RegisterUnaryCallbackHandler? registerUnaryCallback,
  RegisterBinaryCallbackHandler? registerBinaryCallback,
  ErrorCallbackHandler? errorCallback,
  ScheduleMicrotaskHandler? scheduleMicrotask,
  CreateTimerHandler? createTimer,
  CreatePeriodicTimerHandler? createPeriodicTimer,
  PrintHandler? print,
  ForkHandler? fork,
}) {
  return ZoneSpecification(
    handleUncaughtError: handleUncaughtError ?? other.handleUncaughtError,
    run: run ?? other.run,
    runUnary: runUnary ?? other.runUnary,
    runBinary: runBinary ?? other.runBinary,
    registerCallback: registerCallback ?? other.registerCallback,
    registerUnaryCallback:
        registerUnaryCallback ?? other.registerUnaryCallback,
    registerBinaryCallback:
        registerBinaryCallback ?? other.registerBinaryCallback,
    errorCallback: errorCallback ?? other.errorCallback,
    scheduleMicrotask: scheduleMicrotask ?? other.scheduleMicrotask,
    createTimer: createTimer ?? other.createTimer,
    createPeriodicTimer: createPeriodicTimer ?? other.createPeriodicTimer,
    print: print ?? other.print,
    fork: fork ?? other.fork,
  );
}

Properties

createPeriodicTimer no setter

(Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration period, void Function(Timer timer) f))? get createPeriodicTimer

A custom Zone.createPeriodicTimer implementation for a new zone.

Implementation

CreatePeriodicTimerHandler? get createPeriodicTimer;

createTimer no setter

(Timer Function(Zone self, ZoneDelegate parent, Zone zone, Duration duration, void Function() f))? get createTimer

A custom Zone.createTimer implementation for a new zone.

Implementation

CreateTimerHandler? get createTimer;

errorCallback no setter

(AsyncError? Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace? stackTrace))? get errorCallback

A custom Zone.errorCallback implementation for a new zone.

Implementation

ErrorCallbackHandler? get errorCallback;

fork no setter

(Zone Function(Zone self, ZoneDelegate parent, Zone zone, ZoneSpecification? specification, Map<Object?, Object?>? zoneValues))? get fork

A custom Zone.handleUncaughtError implementation for a new zone.

Implementation

ForkHandler? get fork;

handleUncaughtError no setter

(void Function(Zone self, ZoneDelegate parent, Zone zone, Object error, StackTrace stackTrace))? get handleUncaughtError

A custom Zone.handleUncaughtError implementation for a new zone.

Implementation

HandleUncaughtErrorHandler? get handleUncaughtError;

hashCode no setter inherited

int get hashCode

The hash code for this object.

A hash code is a single integer which represents the state of the object that affects operator == comparisons.

All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

Inherited from Object.

Implementation

external int get hashCode;

print no setter

(void Function(Zone self, ZoneDelegate parent, Zone zone, String line))? get print

A custom Zone.print implementation for a new zone.

Implementation

PrintHandler? get print;

registerBinaryCallback no setter

(R Function(T1, T2) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f))? get registerBinaryCallback

A custom Zone.registerBinaryCallback implementation for a new zone.

Implementation

RegisterBinaryCallbackHandler? get registerBinaryCallback;

registerCallback no setter

(R Function() Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? get registerCallback

A custom Zone.registerCallback implementation for a new zone.

Implementation

RegisterCallbackHandler? get registerCallback;

registerUnaryCallback no setter

(R Function(T) Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f))? get registerUnaryCallback

A custom Zone.registerUnaryCallback implementation for a new zone.

Implementation

RegisterUnaryCallbackHandler? get registerUnaryCallback;

run no setter

(R Function(Zone self, ZoneDelegate parent, Zone zone, R Function() f))? get run

A custom Zone.run implementation for a new zone.

Implementation

RunHandler? get run;

runBinary no setter

(R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T1 arg1, T2 arg2) f, T1 arg1, T2 arg2))? get runBinary

A custom Zone.runBinary implementation for a new zone.

Implementation

RunBinaryHandler? get runBinary;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

runUnary no setter

(R Function(Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f, T arg))? get runUnary

A custom Zone.runUnary implementation for a new zone.

Implementation

RunUnaryHandler? get runUnary;

scheduleMicrotask no setter

(void Function(Zone self, ZoneDelegate parent, Zone zone, void Function() f))? get scheduleMicrotask

A custom Zone.scheduleMicrotask implementation for a new zone.

Implementation

ScheduleMicrotaskHandler? get scheduleMicrotask;

Methods

noSuchMethod() inherited

dynamic noSuchMethod(Invocation invocation)

Invoked when a nonexistent method or property is accessed.

A dynamic member invocation can attempt to call a member which doesn't exist on the receiving object. Example:

dynamic object = 1;
object.add(42); // Statically allowed, run-time error

This invalid code will invoke the noSuchMethod method of the integer 1 with an Invocation representing the .add(42) call and arguments (which then throws).

Classes can override noSuchMethod to provide custom behavior for such invalid dynamic invocations.

A class with a non-default noSuchMethod invocation can also omit implementations for members of its interface. Example:

class MockList<T> implements List<T> {
  noSuchMethod(Invocation invocation) {
    log(invocation);
    super.noSuchMethod(invocation); // Will throw.
  }
}
void main() {
  MockList().add(42);
}

This code has no compile-time warnings or errors even though the MockList class has no concrete implementation of any of the List interface methods. Calls to List methods are forwarded to noSuchMethod, so this code will log an invocation similar to Invocation.method(#add, [42]) and then throw.

If a value is returned from noSuchMethod, it becomes the result of the original invocation. If the value is not of a type that can be returned by the original invocation, a type error occurs at the invocation.

The default behavior is to throw a NoSuchMethodError.

Inherited from Object.

Implementation

@pragma("vm:entry-point")
@pragma("wasm:entry-point")
external dynamic noSuchMethod(Invocation invocation);

toString() inherited

String toString()

A string representation of this object.

Some classes have a default textual representation, often paired with a static parse function (like int.parse). These classes will provide the textual representation as their string representation.

Other classes have no meaningful textual representation that a program will care about. Such classes will typically override toString to provide useful information when inspecting the object, mainly for debugging or logging.

Inherited from Object.

Implementation

external String toString();

Operators

operator ==() inherited

bool operator ==(Object other)

The equality operator.

The default behavior for all Objects is to return true if and only if this object and other are the same object.

Override this method to specify a different equality relation on a class. The overriding method must still be an equivalence relation. That is, it must be:

• Total: It must return a boolean for all arguments. It should never throw.

• Reflexive: For all objects o, o == o must be true.

• Symmetric: For all objects o1 and o2, o1 == o2 and o2 == o1 must either both be true, or both be false.

• Transitive: For all objects o1, o2, and o3, if o1 == o2 and o2 == o3 are true, then o1 == o3 must be true.

The method should also be consistent over time, so whether two objects are equal should only change if at least one of the objects was modified.

If a subclass overrides the equality operator, it should override the hashCode method as well to maintain consistency.

Inherited from Object.

Implementation

external bool operator ==(Object other);