PHP中abstract种中有abstract方法是否最先执行abstract方法，然后才执行其他方法

程序员文章站 2022-05-24 20:05:04

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PHP中abstract类中有abstract方法是否最先执行abstract方法，然后才执行其他方法？
rt



abstract class Node {

		private $debugMessages;


		public function __construct() {

			$this->debugMessages = array();

			$this->debug(__CLASS__.' constructor called.');

		}


		public function __destruct() {

			$this->debug(__CLASS__.' destructor called.');

			$this->dumpDebug();

		}


		protected function debug($msg) {

			$this->debugMessages[] = $msg;

		}


		private function dumpDebug() {

			echo implode('
', $this->debugMessages);

		}


		public abstract function getView();

	}



	class ForumTopic extends Node {

		private $debugMessages;


		public function __construct() {

			parent::__construct();

			$this->debug(__CLASS__.' constructor called.');

		}


		public function __destruct() {

			$this->debug(__CLASS__.' destructor called.');

			parent::__destruct();

		}


		public function getView() {

			return 'This is a view into '.__CLASS__.'
';

		}

	}


	$forum = new ForumTopic();

	echo $forum->getView();

执行结果：
This is a view into ForumTopic
Node constructor called.
ForumTopic constructor called.
ForumTopic destructor called.
Node destructor called.

但没有new ForumTopic()怎么能够调用执行getView()？

php destructor constructor function class
------解决方案--------------------
执行顺序:
ForumTopic::__construct()
Node::__construct()
Node::debug()
ForumTopic::debug()
ForumTopic::getView()
ForumTopic::__destruct()
ForumTopic::debug()
Node::__destruct()
Node::debug()
Node::dumpDebug()
------解决方案--------------------
不知道你想说啥，哪个先调用就执行哪个。
你是先执行echo $forum->getView();所以先输出：This is a view into ForumTopic
在对象的销毁的时候，父类析构函数把$debugMessages中的所有数据打印出来了。就下面那样：
Node constructor called.
ForumTopic constructor called.
ForumTopic destructor called.
Node destructor called.

__CLASS__指是的当前类

get_class($obj)指的是实例$obj的类

------解决方案--------------------
如果你把
protected function debug($msg) {
$this->debugMessages[] = $msg;
}
改成
protected function debug($msg) {
echo $msg;
}
你就可以看到真正的执行顺序

------解决方案--------------------

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