PHP Observer Pattern Disadvantages of Observer Pattern Observer Pattern Code Observer Pattern Classes

What I understand about the observer pattern is that when we trigger an event, we want to tell the object I want to tell this operation and let them all perform this operation, which is to bind them to this event.

1. Define a base class (used to add observers, which are the objects I want to notify, and notify observers)

EventGenerator.php

<code><span><span><?php </span><span>abstract</span><span><span>class</span><span>EventGenerator</span>
{</span><span>//存储观察者，因为可以有多个要通知的对象，所以是一个数组</span><span>private</span><span>$observers</span> = <span>array</span>();
    <span>//添加观察者，也就是我想要通知的对象</span><span>public</span><span><span>function</span><span>addObserver</span><span>(<span>$observer</span>)</span>
    {</span><span>$this</span>->observers[] = <span>$observer</span>;
    }
    <span>//通知观察者</span><span>public</span><span><span>function</span><span>notify</span><span>()</span>
    {</span><span>//取出所有的对象去执行操作</span><span>foreach</span>(<span>$this</span>->observers <span>as</span><span>$observer</span>)
        {
            <span>//这里我写一个update方法，这里就要求我所有的通知对象必须要有update操作，所以一会我会定义一个借口，让所有的观察者强制实现这个方法</span><span>$observer</span>->update();
        }
    }
}


<span>?></span></span></span></code>

Define an interface file for all observers to implement update method Observer.php

<code><span><span><?php </span><span><span>interface</span><span>Observer</span>
{</span><span><span>function</span><span>update</span><span>()</span>;</span>
}

<span>?></span></span></span></code>

defines the file that implements the observer pattern Event.php

<code><span><?php </span>
header(<span>'Content-Type:text/html;charset=utf-8'</span>);
define(<span>'BASEDIR'</span>, __DIR___);
<span>require</span><span>'Config.php'</span>;
spl_autoload_register(<span>'Config::autoload'</span>);

<span>//定义事件类继承基类</span><span><span>class</span><span>Event</span><span>extends</span><span>EventGenerator</span>
{</span><span>//当触发这个事件的时候通知所有的观察者</span><span>public</span><span><span>function</span><span>trigger</span><span>()</span>
    {</span><span>echo</span><span>'我要开始更新了啊！<br>\n'</span>;
        <span>//基类的通知方法</span><span>$this</span>->notify();
    }
}
<span>//添加观察者1</span><span><span>class</span><span>Observer1</span><span>implements</span><span>Observer</span>
{</span><span>public</span><span><span>function</span><span>update</span><span>()</span>
    {</span><span>echo</span><span>'我是观察者1，我收到你的通知了！我要干我该干的了！<br>\n'</span>;
    }
}
<span>//添加观察者2</span><span><span>class</span><span>Observer2</span><span>implements</span><span>Observer</span>
{</span><span>public</span><span><span>function</span><span>update</span><span>()</span>
    {</span><span>echo</span><span>'我是观察者2，我收到你的通知了！我要干我该干的了！<br>\n'</span>;
    }
}
<span>//下面就要开始测试了！</span><span>$event</span> = <span>new</span> Event();
<span>//添加观察者到这个事件里</span><span>$event</span>->addObserver(<span>new</span> Observer1);
<span>$event</span>->addObserver(<span>new</span> Observer2);
<span>//执行trigger操作</span><span>$event</span>->trigger();
<span>//这时候就会显示！</span><span>//我要开始更新了啊！</span><span>//我是观察者1，我收到你的通知了！我要干我该干的了！</span><span>//我是观察者2，我收到你的通知了！我要干我该干的了！</span><span>?></span></span></code>

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The above introduces the PHP observer mode, including the observer mode and PHP content. I hope it will be helpful to friends who are interested in PHP tutorials.