AsyncIterator

AsyncIterator simplifies writing asynchronous iteration tasks, such as for-eaching an iterator.

/** @var Plugin $plugin */
$handler = new AsyncIterator($plugin->getScheduler());

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AsyncIterator::forEach traverses forward over an Iterator type and notifies handlers in the order of insertion. Handlers can be added to a forEach task by feeding a Closure to AsyncIterator::forEach()::as(), having the signature function(TKey $key, TValue $value) : AsyncForeachResult.

$handler->forEach(new ArrayIterator([1, 2]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo "First ", $value;
	return AsyncForeachResult::CONTINUE();
})
->as(function(int $key, int $value) : AsyncForeachResult{
	echo "Second ", $value;
	return AsyncForeachResult::CONTINUE();
});

First 1
Second 1
First 2
Second 2

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By default, AsyncIterator::forEach traverses over 10 entries each tick. This can be changed by overriding the default parameter values of the method.

$entries_per_tick = 4;
$sleep_time = 1; // in ticks
AsyncIterator::forEach(new InfiniteIterator(new ArrayIterator([1, 2, 3])), $entries_per_tick, $sleep_time)
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value, ", ";
	return AsyncForeachResult::CONTINUE();
});

# First Tick:
1, 2, 3, 1

# Second Tick:
2, 3, 1, 2

...

---

Completion listeners are triggered when a foreach task successfully completes. This is determined by the return value of Iterator::valid() (i.e., $completed = !Iterator::valid()) of the iterator that is passed to AsyncIterator::forEach.

$handler->forEach(new ArrayIterator([1, 2, 3]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value;
	return AsyncForeachResult::CONTINUE();
})
->onCompletion(function() : void{ echo "Completed"; })

---

Handlers have the ability to either continue, interrupt or cancel the traversal by returning either AsyncForeachResult::CONTINUE(), AsyncForeachResult::INTERRUPT() or AsyncForeachResult::CANCEL() respectively. When interrupted, a forEach task will not traverse the iterator anymore and notify interrupt listeners immediately. However, when cancelled, a forEach task will notify no listeners and immediately dispose the task away.

$handler->forEach(new ArrayIterator([1, 2, 3]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value;
	return $value === 2 ? AsyncForeachResult::INTERRUPT() : AsyncForeachResult::CONTINUE();
})
->onCompletion(function() : void{ echo "Completed"; })
->onInterruption(function() : void{ echo "Interrupted"; });

1
2
Interrupted

$handler->forEach(new ArrayIterator([1, 2, 3]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value;
	return AsyncForeachResult::CONTINUE();
})
->onCompletion(function() : void{ echo "Completed"; })
->onInterruption(function() : void{ echo "Interrupted"; });

1
2
3
Completed

---

Interruption of a forEach task can also occur externally (outside the handler) by calling the interrupt() method on the return value of forEach.

$foreach_task = $handler->forEach(new ArrayIterator([1, 2, 3]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value;
	return AsyncForeachResult::CONTINUE();
})
->onCompletion(function() : void{ echo "Completed"; })
->onInterruption(function() : void{ echo "Interrupted"; });

TaskScheduler::scheduleDelayedTask(function() use($foreach_task) : void{
	$foreach_task->interrupt();
}, ticks: 2);

1
2
Interrupted

---

A `forEach` task may be cancelled by calling the `cancel()` method on the return value of `forEach`, causing no interrupt or completion listeners to be notified.

$foreach_task = $handler->forEach(new ArrayIterator([1, 2, 3]))
->as(function(int $key, int $value) : AsyncForeachResult{
	echo $value;
	return AsyncForeachResult::CONTINUE();
})
->onCompletion(function() : void{ echo "Completed"; })
->onInterruption(function() : void{ echo "Interrupted"; });

TaskScheduler::scheduleDelayedTask(function() use($foreach_task) : void{
	$foreach_task->cancel();
}, ticks: 2);

1
2

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