doctrine2/lib/Doctrine/Common/EventArgs.php

<?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()}.
 *
 * @author      Konsta Vesterinen <kvesteri@cc.hut.fi>
 * @author      Roman Borschel
 * @license     http://www.opensource.org/licenses/lgpl-license.php LGPL
 * @link        www.doctrine-project.org
 * @since       2.0
 * @version     $Revision$
 */
class EventArgs
{
    private static $_emptyEventArgsInstance;
    
    /**
     * Gets the single, empty EventArgs instance.
     * 
     * @return EventArgs
     */
    public static function getEmptyInstance()
    {
        if ( ! self::$_emptyEventArgsInstance) {
            self::$_emptyEventArgsInstance = new EventArgs;
        }
        return self::$_emptyEventArgsInstance;
    }
}