<?php

/*

 *  $Id$

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * This software consists of voluntary contributions made by many individuals

 * and is licensed under the LGPL. For more information, see

 * <http://www.doctrine-project.org>.

 */

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}.

 *

 * @license http://www.opensource.org/licenses/lgpl-license.php LGPL

 * @link    www.doctrine-project.org

 * @since   2.0

 * @version $Revision: 3938 $

 * @author  Guilherme Blanco <guilhermeblanco@hotmail.com>

 * @author  Jonathan Wage <jonwage@gmail.com>

 * @author  Roman Borschel <roman@code-factory.org>

 */

class EventArgs

{

    /**

     * @var EventArgs Single instance of EventArgs

     * @static

     */

    private static $_emptyEventArgsInstance;

    /**

     * 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)

     *

     * @see EventManager::dispatchEvent

     * @link http://msdn.microsoft.com/en-us/library/system.eventargs.aspx

     * @static

     * @return EventArgs

     */

    public static function getEmptyInstance()

    {

        if ( ! self::$_emptyEventArgsInstance) {

            self::$_emptyEventArgsInstance = new EventArgs;

        }

        return self::$_emptyEventArgsInstance;

    }

}