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1 <?php
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2 /*
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3 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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4 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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5 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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6 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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7 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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8 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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9 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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10 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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11 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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12 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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13 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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14 *
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15 * This software consists of voluntary contributions made by many individuals
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16 * and is licensed under the MIT license. For more information, see
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17 * <http://www.doctrine-project.org>.
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18 */
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19
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20 namespace Doctrine\Common;
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21
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22 /**
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23 * EventArgs is the base class for classes containing event data.
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24 *
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25 * This class contains no event data. It is used by events that do not pass state
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26 * information to an event handler when an event is raised. The single empty EventArgs
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27 * instance can be obtained through {@link getEmptyInstance}.
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28 *
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29 * @link www.doctrine-project.org
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30 * @since 2.0
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31 * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
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32 * @author Jonathan Wage <jonwage@gmail.com>
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33 * @author Roman Borschel <roman@code-factory.org>
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34 */
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35 class EventArgs
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36 {
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37 /**
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38 * Single instance of EventArgs.
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39 *
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40 * @var EventArgs
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41 */
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42 private static $_emptyEventArgsInstance;
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43
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44 /**
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45 * Gets the single, empty and immutable EventArgs instance.
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46 *
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47 * This instance will be used when events are dispatched without any parameter,
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48 * like this: EventManager::dispatchEvent('eventname');
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49 *
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50 * The benefit from this is that only one empty instance is instantiated and shared
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51 * (otherwise there would be instances for every dispatched in the abovementioned form).
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52 *
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53 * @see EventManager::dispatchEvent
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54 *
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55 * @link http://msdn.microsoft.com/en-us/library/system.eventargs.aspx
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56 *
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57 * @return EventArgs
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58 */
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59 public static function getEmptyInstance()
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60 {
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61 if ( ! self::$_emptyEventArgsInstance) {
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62 self::$_emptyEventArgsInstance = new EventArgs;
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63 }
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64
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65 return self::$_emptyEventArgsInstance;
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66 }
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67 }
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