Chris@0: <?php
Chris@0: /*
Chris@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
Chris@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
Chris@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
Chris@0:  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
Chris@0:  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
Chris@0:  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
Chris@0:  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
Chris@0:  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
Chris@0:  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
Chris@0:  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
Chris@0:  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Chris@0:  *
Chris@0:  * This software consists of voluntary contributions made by many individuals
Chris@0:  * and is licensed under the MIT license. For more information, see
Chris@0:  * <http://www.doctrine-project.org>.
Chris@0:  */
Chris@0: 
Chris@0: namespace Doctrine\Common;
Chris@0: 
Chris@0: /**
Chris@0:  * EventArgs is the base class for classes containing event data.
Chris@0:  *
Chris@0:  * This class contains no event data. It is used by events that do not pass state
Chris@0:  * information to an event handler when an event is raised. The single empty EventArgs
Chris@0:  * instance can be obtained through {@link getEmptyInstance}.
Chris@0:  *
Chris@0:  * @link   www.doctrine-project.org
Chris@0:  * @since  2.0
Chris@0:  * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
Chris@0:  * @author Jonathan Wage <jonwage@gmail.com>
Chris@0:  * @author Roman Borschel <roman@code-factory.org>
Chris@0:  */
Chris@0: class EventArgs
Chris@0: {
Chris@0:     /**
Chris@0:      * Single instance of EventArgs.
Chris@0:      *
Chris@0:      * @var EventArgs
Chris@0:      */
Chris@0:     private static $_emptyEventArgsInstance;
Chris@0: 
Chris@0:     /**
Chris@0:      * Gets the single, empty and immutable EventArgs instance.
Chris@0:      *
Chris@0:      * This instance will be used when events are dispatched without any parameter,
Chris@0:      * like this: EventManager::dispatchEvent('eventname');
Chris@0:      *
Chris@0:      * The benefit from this is that only one empty instance is instantiated and shared
Chris@0:      * (otherwise there would be instances for every dispatched in the abovementioned form).
Chris@0:      *
Chris@0:      * @see EventManager::dispatchEvent
Chris@0:      *
Chris@0:      * @link http://msdn.microsoft.com/en-us/library/system.eventargs.aspx
Chris@0:      *
Chris@0:      * @return EventArgs
Chris@0:      */
Chris@0:     public static function getEmptyInstance()
Chris@0:     {
Chris@0:         if ( ! self::$_emptyEventArgsInstance) {
Chris@0:             self::$_emptyEventArgsInstance = new EventArgs;
Chris@0:         }
Chris@0: 
Chris@0:         return self::$_emptyEventArgsInstance;
Chris@0:     }
Chris@0: }