StreamSink<S> abstract interface

abstract interface class StreamSink<S> implements EventSink<S>, StreamConsumer<S>

A object that accepts stream events both synchronously and asynchronously.

A StreamSink combines the methods from StreamConsumer and EventSink.

The EventSink methods can't be used while the addStream is called. As soon as the addStream's Future completes with a value, the EventSink methods can be used again.

If addStream is called after any of the EventSink methods, it'll be delayed until the underlying system has consumed the data added by the EventSink methods.

When EventSink methods are used, the done Future can be used to catch any errors.

When close is called, it will return the done Future.

Implemented types

• EventSink<T>
• StreamConsumer<S>

Implementers

• IOSink
• StreamController<T>
• WebSocket

Properties

done no setter

Future<dynamic> get done

Return a future which is completed when the StreamSink is finished.

If the StreamSink fails with an error, perhaps in response to adding events using add, addError or close, the done future will complete with that error.

Otherwise, the returned future will complete when either:

• all events have been processed and the sink has been closed, or
• the sink has otherwise been stopped from handling more events (for example by canceling a stream subscription).

Implementation

Future get done;

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;

runtimeType no setter inherited

Type get runtimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

Methods

add() inherited

void add(S event)

Adds a data event to the sink.

Must not be called on a closed sink.

Inherited from EventSink.

Implementation

void add(T event);

addError() inherited

void addError(Object error, [StackTrace? stackTrace])

Adds an error to the sink.

Must not be called on a closed sink.

Inherited from EventSink.

Implementation

void addError(Object error, [StackTrace? stackTrace]);

addStream() inherited

Future<dynamic> addStream(Stream<S> stream)

Consumes the elements of stream.

Listens on stream and does something for each event.

Returns a future which is completed when the stream is done being added, and the consumer is ready to accept a new stream. No further calls to addStream or close should happen before the returned future has completed.

The consumer may stop listening to the stream after an error, it may consume all the errors and only stop at a done event, or it may be canceled early if the receiver don't want any further events.

If the consumer stops listening because of some error preventing it from continuing, it may report this error in the returned future, otherwise it will just complete the future with null.

Inherited from StreamConsumer.

Implementation

Future addStream(Stream<S> stream);

close() override

Future<dynamic> close()

Tells the stream sink that no further streams will be added.

This allows the stream sink to complete any remaining work and release resources that are no longer needed

Returns a future which is completed when the stream sink has shut down. If cleaning up can fail, the error may be reported in the returned future, otherwise it completes with null.

Returns the same future as done.

The stream sink may close before the close method is called, either due to an error or because it is itself providing events to someone who has stopped listening. In that case, the done future is completed first, and the close method will return the done future when called.

Unifies StreamConsumer.close and EventSink.close which both mark their object as not expecting any further events.

Implementation

Future close();

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);