Waiter<T> class

Manages a collection of operations for deferred, batched execution.

Unlike Future.wait, which requires a list of already-running Future instances, a Waiter collects WaiterOperation descriptors that have not yet been executed. This lets you build up a queue of tasks from different parts of your application and then run them all at once by calling wait.

Per-isolate model. A Waiter instance is owned by exactly one isolate. The internal queue is a mutable List, so two isolates must each construct their own Waiter — passing a populated Waiter across a SendPort is rejected at runtime unless every operation's run is a top-level/static function and the receiving isolate is willing to reconstruct the wrapper. Use operations to extract a sendable snapshot when you need to hand work off to a worker isolate.

Web compatibility. Everything here is pure Dart with no dart:isolate or dart:io dependencies, so it works unchanged on Flutter web, dart2js, dartdevc, and the VM.

{@tool snippet}

final waiter = Waiter<String>();

// Define tasks without running them.
waiter.addFn(() => 'Sync task complete');
waiter.addFn(() async {
  await Future.delayed(Duration(milliseconds: 20));
  return 'Async task complete';
});

// Execute the entire batch.
final results = await waiter.wait();
print(results); // (Sync task complete, Async task complete)

{@end-tool}

Constructors

Waiter({_TOnErrorCallback? onError, Iterable<WaiterOperation<T>> operations = const <Never>[]})

Creates a waiter to queue and manage deferred operations.

Properties

hashCode → int

The hash code for this object.

no setter, inherited

operations → List<WaiterOperation<T>>

A read-only snapshot of the pending operations.

no setter

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

add(WaiterOperation<T> operation) → void

Adds a deferred operation to the queue.

addAll(Iterable<WaiterOperation<T>> operations) → void

Adds multiple deferred operations to the queue.

addFn(FutureOr<T> fn(), {String? id}) → void

Adds a bare function as a deferred operation. Convenience shortcut for add(WaiterOperation(fn, id: id)); behaves identically except the caller does not have to construct the wrapper.

clear() → void

Removes all pending operations from the queue.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

remove(WaiterOperation<T> operation) → void

Removes a specific operation from the queue.

removeWhere(bool test(WaiterOperation<T> op)) → void

Removes operations matching test.

toString() → String

A string representation of this object.

inherited

wait({_TOnErrorCallback? onError, bool eagerError = true}) → FutureOr<Iterable<T>>

Executes all queued operations and returns their results.

Operators

operator ==(Object other) → bool

The equality operator.

inherited