}
}
public function buy()
{
//stub actions of buying
$this->notifyObserver('purchased');
}
}
class buyCDNotifyStreamObserver
{
public function update(CD $cd)
{
$activity = "The CD named {$cd->title} by ";
$activity .= "{$cd->band} was just purchased.";
activityStream::addNewItem($activity);
}
}
class activityStream
{
public static function addNewItem($item)
{
//stub functions
print $item;
}
}
$title = 'Waste of a Rib';
$band = 'Never Again';
$cd = new CD($title, $band);
$observer = new buyCDNotifyStreamObserver();
$cd->attachObserver('purchased', $observer);
$cd->buy();
}
public function buy()
{
$this->notifyObserver("purchased");
}
}
//观察者类 后台处理
class buyCDNotifyStreamObserver
{
public function update(CD $cd)
{
$activity = "The CD named {$cd->title} by ";
$activity .= "{$cd->band} was just purchased.";
activityStream::addNewItem($activity);
}
}
//消息同事类 前台输出
class activityStream
{
public static function addNewItem($item)
{
print $item;
}
}
//测试实例
$title = "Waste of a Rib";
$band = "Never Again";
$cd = new CD($title, $band);
$observer = new buyCDNotifyStreamObserver();
$cd->attachObserver("purchased", $observer);
$cd->buy();