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<?php
declare(strict_types=1);
namespace Doctrine\Common;
/**
* EventArgs is the base class for classes containing event data.
*
* This class contains no event data. It is used by events that do not pass state
* information to an event handler when an event is raised. The single empty EventArgs
* instance can be obtained through {@link getEmptyInstance}.
*/
class EventArgs
{
/**
* Single instance of EventArgs.
*/
private static EventArgs|null $emptyEventArgsInstance = null;
/**
* Gets the single, empty and immutable EventArgs instance.
*
* This instance will be used when events are dispatched without any parameter,
* like this: EventManager::dispatchEvent('eventname');
*
* The benefit from this is that only one empty instance is instantiated and shared
* (otherwise there would be instances for every dispatched in the abovementioned form).
*
* @link https://msdn.microsoft.com/en-us/library/system.eventargs.aspx
* @see EventManager::dispatchEvent
*/
public static function getEmptyInstance(): EventArgs
{
return self::$emptyEventArgsInstance ??= new EventArgs();
}
}
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