1 <?php

     2 /*

     3  *  $Id$

     4  *

     5  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

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

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

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

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

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

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

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

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

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

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

    16  *

    17  * This software consists of voluntary contributions made by many individuals

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

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

    20  */

    21 

    22 namespace Doctrine\Common;

    23 

    24 /**

    25  * EventArgs is the base class for classes containing event data.

    26  *

    27  * This class contains no event data. It is used by events that do not pass state

    28  * information to an event handler when an event is raised. The single empty EventArgs

    29  * instance can be obtained through {@link getEmptyInstance}.

    30  *

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

    32  * @link    www.doctrine-project.org

    33  * @since   2.0

    34  * @version $Revision: 3938 $

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

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

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

    38  */

    39 class EventArgs

    40 {

    41     /**

    42      * @var EventArgs Single instance of EventArgs

    43      * @static

    44      */

    45     private static $_emptyEventArgsInstance;

    46 

    47     /**

    48      * Gets the single, empty and immutable EventArgs instance.

    49      *

    50      * This instance will be used when events are dispatched without any parameter,

    51      * like this: EventManager::dispatchEvent('eventname');

    52      *

    53      * The benefit from this is that only one empty instance is instantiated and shared

    54      * (otherwise there would be instances for every dispatched in the abovementioned form)

    55      *

    56      * @see EventManager::dispatchEvent

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

    58      * @static

    59      * @return EventArgs

    60      */

    61     public static function getEmptyInstance()

    62     {

    63         if ( ! self::$_emptyEventArgsInstance) {

    64             self::$_emptyEventArgsInstance = new EventArgs;

    65         }

    66 

    67         return self::$_emptyEventArgsInstance;

    68     }

    69 }