PHP设计模式学习笔记： 责任链模式（Chain of Responsibility）

// 抽象书本类  abstract class AbstractBookTopic {      abstract function getTopic();      abstract function getTitle();      abstract function setTitle($title_in);  }    // 书本类，继承自抽象书本类  class BookTopic extends AbstractBookTopic {      private $topic;      private $title;        function __construct($topic_in) {        $this->topic = $topic_in;        $this->title = NULL;      }        function getTopic() {        return $this->topic;      }        function getTitle() {        if (NULL != $this->title) {          return $this->title;        } else {          return '目前没有标题';        }      }        function setTitle($title_in) {        $this->title = $title_in;      }  }    // 子书本类，继承自抽象书本类  class BookSubTopic extends AbstractBookTopic {      private $topic;      private $parentTopic;      private $title;        function __construct($topic_in, BookTopic $parentTopic_in) {        $this->topic = $topic_in;        $this->parentTopic = $parentTopic_in;        $this->title = NULL;      }        function getTopic() {        return $this->topic;      }        function getParentTopic() {        return $this->parentTopic;      }           function getTitle() {        if (NULL != $this->title) {          return $this->title;        } else {          return $this->parentTopic->getTitle();        }      }        function setTitle($title_in) {        $this->title = $title_in;      }  }    // 子子书本类，继承自抽象书本类  class BookSubSubTopic extends AbstractBookTopic {      private $topic;      private $parentTopic;      private $title;        function __construct($topic_in, BookSubTopic $parentTopic_in) {        $this->topic = $topic_in;        $this->parentTopic = $parentTopic_in;        $this->title = NULL;      }        function getTopic() {        return $this->topic;      }        function getParentTopic() {        return $this->parentTopic;      }           function getTitle() {        if (NULL != $this->title) {          return $this->title;        } else {          return $this->parentTopic->getTitle();        }      }        function setTitle($title_in) {        $this->title = $title_in;      }  }      writeln("开始测试责任链模式");    writeln("");      $bookTopic = new BookTopic("魔法");    writeln("bookTopic设置标题前:");    writeln("主题: " . $bookTopic->getTopic());    writeln("标题: " . $bookTopic->getTitle());    writeln("");      $bookTopic->setTitle("哈利波特与魔法石");    writeln("bookTopic设置标题后: ");    writeln("主题: " . $bookTopic->getTopic());    writeln("标题: " . $bookTopic->getTitle());    writeln("");       $bookSubTopic = new BookSubTopic("英国魔法", $bookTopic);    writeln("bookSubTopic标题设置前: ");    writeln("主题: " . $bookSubTopic->getTopic());    writeln("标题: " . $bookSubTopic->getTitle());    writeln("");      $bookSubTopic->setTitle("哈利波特与混血王子");    writeln("bookSubTopic标题设置后: ");    writeln("主题: ". $bookSubTopic->getTopic());    writeln("标题: ". $bookSubTopic->getTitle());    writeln("");       $bookSubSubTopic = new BookSubSubTopic("英国现代魔法", $bookSubTopic);    writeln("bookSubSubTopic标题设置前: ");    writeln("主题: " . $bookSubSubTopic->getTopic());    writeln("标题: " . $bookSubSubTopic->getTitle());    writeln("");      $bookSubTopic->setTitle(NULL);    writeln("bookSubSubTopic、 bookSubTopic都没有设置标题:");    writeln("主题: " . $bookSubSubTopic->getTopic());    writeln("标题: " . $bookSubSubTopic->getTitle());    writeln("");      writeln("结束测试责任链模式");      function writeln($line_in) {      echo $line_in.PHP_EOL;    }

开始测试责任链模式    bookTopic设置标题前:  主题: 魔法  标题: 目前没有标题    bookTopic设置标题后:   主题: 魔法  标题: 哈利波特与魔法石    bookSubTopic标题设置前:   主题: 英国魔法  标题: 哈利波特与魔法石    bookSubTopic标题设置后:   主题: 英国魔法  标题: 哈利波特与混血王子    bookSubSubTopic标题设置前:   主题: 英国现代魔法  标题: 哈利波特与混血王子    bookSubSubTopic、 bookSubTopic都没有设置标题:  主题: 英国现代魔法  标题: 哈利波特与魔法石    结束测试责任链模式