前面阅读了Yii2的两个基本类Object和Component，了解了Yii的三个重要概念属性、事件、行为，下面开始阅读Event类，Event类是所有事件类的基类：
1 <?php
2 /**
3 * @link http://www.yiiframework.com/
4 * @copyright Copyright (c) 2008 Yii Software LLC
5 * @license http://www.yiiframework.com/license/
6 */
7
8 namespace yii\base;
9
10 /**
11 * Event is the base class for all event classes.
12 * Event 是所有事件类的基类，是对Component的深化
13 *
14 * It encapsulates the parameters associated with an event.
15 * The [[sender]] property describes who raises the event.
16 * And the [[handled]] property indicates if the event is handled.
17 * If an event handler sets [[handled]] to be true, the rest of the
18 * uninvoked handlers will no longer be called to handle the event.
19 *
20 * Additionally, when attaching an event handler, extra data may be passed
21 * and be available via the [[data]] property when the event handler is invoked.
22 *
23 * @author Qiang Xue <[email protected]>
24 * @since 2.0
25 */
26 class Event extends Object
27 {
28 /**
29 * @var string the event name. This property is set by [[Component::trigger()]] and [[trigger()]].
30 * Event handlers may use this property to check what event it is handling.
31 * 事件的名字，通过[[Component::trigger()]] 和 [[trigger()]]方法设置，事件处理程序通过这个属性类检查处理的事件
32 */
33 public $name;
34 /**
35 * @var object the sender of this event. If not set, this property will be
36 * set as the object whose "trigger()" method is called.
37 * This property may also be a `null` when this event is a
38 * class-level event which is triggered in a static context.
39 *
40 * 触发事件的对象，如果未设置，则设置为调用"trigger()"方法的对象，如果是在静态环境下触发的类级别的事件，怎为空
41 */
42 public $sender;
43 /**
44 * @var boolean whether the event is handled. Defaults to false.
45 * When a handler sets this to be true, the event processing will stop and
46 * ignore the rest of the uninvoked event handlers.
47 *
48 * 记录事件是否已被处理，当 handled 被设置为 true 时，执行到这个 event 的时候，会停止，并忽略剩下的 event
49 */
50 public $handled = false;
51 /**
52 * @var mixed the data that is passed to [[Component::on()]] when attaching an event handler.
53 * Note that this varies according to which event handler is currently executing.
54 * 事件加载时传入的数据，对应当前执行的事件处理程序
55 */
56 public $data;
57
58 /**
59 * @var array contains all globally registered event handlers.
60 * 存储所有的 event，因为是 static 的属性，所有的 event 对象/类都共享这一份数据
61 */
62 private static $_events = [];
63
64
65 /**
66 * Attaches an event handler to a class-level event.
67 * 为一个类添加事件
68 *
69 * When a class-level event is triggered, event handlers attached
70 * to that class and all parent classes will be invoked.
71 *
72 * For example, the following code attaches an event handler to `ActiveRecord`‘s
73 * `afterInsert` event:
74 *
75 * ```php
76 * Event::on(ActiveRecord::className(), ActiveRecord::EVENT_AFTER_INSERT, function ($event) {
77 * Yii::trace(get_class($event->sender) . ‘ is inserted.‘);
78 * });
79 * ```
80 *
81 * The handler will be invoked for EVERY successful ActiveRecord insertion.
82 *
83 * For more details about how to declare an event handler, please refer to [[Component::on()]].
84 *
85 * @param string|object $class 定义的类级别的对象或者类名称.
86 * @param string $name 事件名
87 * @param callable $handler 事件处理程序.
88 * @param mixed $data 数据.
89 * When the event handler is invoked, this data can be accessed via [[Event::data]].
90 * @param boolean $append whether to append new event handler to the end of the existing
91 * handler list. If false, the new handler will be inserted at the beginning of the existing
92 * handler list.
93 * @see off()
94 */
95 public static function on($class, $name, $handler, $data = null, $append = true)
96 {
97 // 去掉 class 最左边的斜线
98 $class = ltrim($class, ‘\\‘);
99 if ($append || empty(self::$_events[$name][$class])) {
100 // 如果 append 为true，就放到 $_events 中名字为 $name 的数组的最后
101 self::$_events[$name][$class][] = [$handler, $data];
102 } else {
103 //否则放到最前面
104 array_unshift(self::$_events[$name][$class], [$handler, $data]);
105 }
106 }
107
108 /**
109 * Detaches an event handler from a class-level event.
110 * [[on()]]方法的反方法，移除一个类的事件
111 * This method is the opposite of [[on()]].
112 *
113 * @param string|object $class 定义的类级别的对象或者类名称.
114 * @param string $name 事件名
115 * @param callable $handler 事件处理程序.
116 * If it is null, all handlers attached to the named event will be removed.
117 * @return boolean whether a handler is found and detached.
118 * @see on()
119 */
120 public static function off($class, $name, $handler = null)
121 {
122 // 去掉 class 最左边的斜线
123 $class = ltrim($class, ‘\\‘);
124 if (empty(self::$_events[$name][$class])) {
125 // 如果不存在该事件，返回false
126 return false;
127 }
128 if ($handler === null) {
129 // 如果 handler 为空，也就是没有规定移除的事件处理程序，直接将该事件移除，即移出所有的是这个名字的事件
130 unset(self::$_events[$name][$class]);
131 return true;
132 } else {
133 $removed = false; //移除标记
134 // 如果 $handler 不为空，遍历 $_events 找到相应的 handler，只移除这个 handler 和 data 组成的数组
135 foreach (self::$_events[$name][$class] as $i => $event) {
136 if ($event[0] === $handler) {
137 unset(self::$_events[$name][$class][$i]);
138 $removed = true;
139 }
140 }
141 if ($removed) {
142 //如果删除成功，调用array_values方法重新赋值，初始化索引
143 self::$_events[$name][$class] = array_values(self::$_events[$name][$class]);
144 }
145
146 return $removed;
147 }
148 }
149
150 /**
151 * Returns a value indicating whether there is any handler attached to the specified class-level event.
152 * Note that this method will also check all parent classes to see if there is any handler attached
153 * to the named event.
154 * 检测在某个类或者对象是否具有某个事件/会同时检测父类
155 *
156 * @param string|object $class 定义的类级别的对象或者类名称.
157 * @param string $name 事件名
158 * @return boolean whether there is any handler attached to the event.
159 */
160 public static function hasHandlers($class, $name)
161 {
162 if (empty(self::$_events[$name])) {
163 //如果不存在，直接返回false
164 return false;
165 }
166 if (is_object($class)) {
167 // 如果是一个 object，就获取其类名 get_class 内置函数，用于获取对象的方法
168 $class = get_class($class);
169 } else {
170 // 如果是一个类名，就去掉 class 最左边的斜杠
171 $class = ltrim($class, ‘\\‘);
172 }
173 //将该类/该对象对应的类的父类以及该类/该对象对应的类实现的接口名称合并到一个数组中
174 $classes = array_merge(
175 [$class],
176 class_parents($class, true),//获取父类的类名
177 class_implements($class, true)//获取当前类和父类实现的所有接口类名
178 );
179 //判断是否存在事件处理程序，存在返回true
180 foreach ($classes as $class) {
181 if (!empty(self::$_events[$name][$class])) {
182 return true;
183 }
184 }
185
186 return false;
187 }
188
189 /**
190 * Triggers a class-level event.
191 * This method will cause invocation of event handlers that are attached to the named event
192 * for the specified class and all its parent classes.
193 * 触发某个类或者对象的某个事件/会同时作用于父类
194 *
195 * @param string|object $class 定义的类级别的对象或者类名称.
196 * @param string $name 事件名
197 * @param Event $event the event parameter. If not set, a default [[Event]] object will be created.
198 */
199 public static function trigger($class, $name, $event = null)
200 {
201 if (empty(self::$_events[$name])) {
202 //如果事件不存在，直接返回
203 return;
204 }
205 if ($event === null) {
206 // 构建Event对象，为传入到handler函数中做准备
207 $event = new static;
208 }
209 $event->handled = false;//事件是否被处理标志
210 $event->name = $name;//事件名
211
212 if (is_object($class)) {
213 if ($event->sender === null) {
214 // 如果 $class 是个对象，并且是 sender 为空，就将 $class 赋给 sender，即 $class 就是触发事件的对象
215 $event->sender = $class;
216 }
217 $class = get_class($class);//取得类名称
218 } else {
219 $class = ltrim($class, ‘\\‘);//去掉类名称左边的斜线
220 }
221 //将该类/该对象对应的类的父类以及该类/该对象对应的类实现的接口名称合并到一个数组中
222 $classes = array_merge(
223 [$class],
224 class_parents($class, true),
225 class_implements($class, true)
226 );
227
228 foreach ($classes as $class) {//遍历所有的类
229 if (!empty(self::$_events[$name][$class])) {//找到符合条件的类
230 foreach (self::$_events[$name][$class] as $handler) {
231 $event->data = $handler[1];//设置data数据
232 call_user_func($handler[0], $event);//调用处理程序
233 if ($event->handled) {//事件是否被处理标志为真，结束执行
234 return;
235 }
236 }
237 }
238 }
239 }
240 }
时间： 2024-12-09 22:46:53