Channel<A>

mixinChannel<A>

A concurrent channel that supports sending and receiving values across fibers, with configurable back-pressure.

A Channel behaves like a bounded queue: producers call send to enqueue values and consumers read them via rill. When the channel is full, send semantically blocks the calling fiber until space is available. When the channel is empty, rill suspends until a value arrives.

Create a channel with one of the factory constructors:

final ch = await Channel.bounded<int>(16).run();
final ch = await Channel.synchronous<int>().run(); // rendezvous
final ch = await Channel.unbounded<int>().run();

Close the channel when no more values will be sent; the consumer rill will terminate after draining any remaining buffered values.

Properties

closed no setter

IO<Unit>getclosed

An IO that blocks until the channel is closed.

Implementation

IO<Unit> get closed;

hashCode no setter inherited

intgethashCode

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;

isClosed no setter

IO<bool>getisClosed

An IO that evaluates to true if the channel has been closed.

Implementation

IO<bool> get isClosed;

rill no setter

Rill<A>getrill

A Rill that emits every value sent to this channel.

The stream suspends when the channel is empty and terminates after the channel is closed and all buffered values have been emitted.

Implementation

Rill<A> get rill;

runtimeType no setter inherited

TypegetruntimeType

A representation of the runtime type of the object.

Inherited from Object.

Implementation

external Type get runtimeType;

sendAll no setter

Rill<Never>Function(Rill<A>)getsendAll

A Pipe that forwards all elements of the input Rill into this channel and closes the channel when the input stream ends.

The pipe terminates as soon as the channel is closed (either by the input ending or by an external close call), discarding any remaining input.

Implementation

Pipe<A, Never> get sendAll;

Methods

close()

IO<Either<ChannelClosed,Unit>>close()

Closes the channel, preventing any further sends.

Consumers will continue to receive buffered values before rill terminates. Returns Left with ChannelClosed if already closed.

Implementation

IO<Either<ChannelClosed, Unit>> close();

closeWithElement()

IO<Either<ChannelClosed,Unit>>closeWithElement(Aa)

Sends a and then closes the channel atomically.

Equivalent to sending a followed by close, but guaranteed to be atomic — no other send can interleave between the two operations. Returns Left with ChannelClosed if the channel was already closed.

Implementation

IO<Either<ChannelClosed, Unit>> closeWithElement(A a);

noSuchMethod() inherited

dynamicnoSuchMethod(Invocationinvocation)

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);

send()

IO<Either<ChannelClosed,Unit>>send(Aa)

Sends a to the channel, blocking if the channel buffer is full.

Returns Right on success, or Left with ChannelClosed if the channel was already closed before or during the send.

Implementation

IO<Either<ChannelClosed, Unit>> send(A a);

toString() inherited

StringtoString()

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();

trySend()

IO<Either<ChannelClosed,bool>>trySend(Aa)

Attempts to send a to the channel without blocking.

Returns Right<true> if the value was enqueued, Right<false> if the buffer was full, or Left with ChannelClosed if the channel is closed.

Implementation

IO<Either<ChannelClosed, bool>> trySend(A a);

Operators

operator ==() inherited

booloperator ==(Objectother)

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);

Static Methods

bounded()

IO<Channel<A>>bounded<A>(intcapacity)

Creates a channel with a fixed-size buffer of capacity elements.

Senders block when the buffer is full and are unblocked in FIFO order as consumers drain elements.

Implementation

static IO<Channel<A>> bounded<A>(int capacity) => _BoundedChannel.create(capacity);

synchronous()

IO<Channel<A>>synchronous<A>()

Creates a synchronous (rendezvous) channel with no internal buffer.

Every send blocks until a consumer is ready to receive, and vice versa. Equivalent to bounded(0).

Implementation

static IO<Channel<A>> synchronous<A>() => bounded(0);

unbounded()

IO<Channel<A>>unbounded<A>()

Creates an unbounded channel that never blocks senders.

Use with care — an unbounded channel can grow without limit if producers outpace consumers.

Implementation

static IO<Channel<A>> unbounded<A>() => bounded(Integer.maxValue);