PHP Design Patterns Learning notes: The responsibility chain model (Chain of Responsibility)

Abstract class Abstraction class Abstractbooktopic {abstract function gettopic ();    Abstract function getTitle (); Abstract function Settitle ($title _in);}    Book class, inherit from abstract book 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 $this->title;      } else {return ' currently has no title ';    }} function Settitle ($title _in) {$this->title = $title _in;    }}//, inheriting from abstract book 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;    }}//Sub-book class, Inherit from abstract book 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 ("Start testing responsibility chain mode");  Writeln ("");  $bookTopic = new Booktopic ("Magic");  Writeln ("Booktopic before setting the title:"); Writeln ("Subject:".  $bookTopic->gettopic ()); Writeln ("title:".  $bookTopic->gettitle ());  Writeln ("");  $bookTopic->settitle ("Harry Potter and the Philosopher's Stone");  Writeln ("Booktopic after setting the title:"); Writeln ("Subject:".  $bookTopic->gettopic ()); Writeln ("title:".  $bookTopic->gettitle ());   Writeln ("");  $bookSubTopic = new Booksubtopic ("English Magic", $bookTopic);  Writeln ("Booksubtopic title pre-set:"); Writeln ("Subject:".  $bookSubTopic->gettopic ()); Writeln ("title:".  $bookSubTopic->gettitle ());  Writeln ("");  $bookSubTopic->settitle ("Harry Potter and the Half-Blood Prince");  Writeln ("Booksubtopic title set After:"); Writeln ("Subject:".  $bookSubTopic->gettopic ()); Writeln ("title:".  $bookSubTopic->gettitle ());   Writeln ("");  $bookSubSubTopic = new Booksubsubtopic ("Modern British Magic", $bookSubTopic);  Writeln ("Booksubsubtopic title pre-set:"); Writeln ("Subject:".  $bookSubSubTopic->gettopic ()); Writeln ("title:".  $bookSubSubTopic->gettitle ());  Writeln (""); $bookSubTopic->settitle (NULL);  Writeln ("Booksubsubtopic, Booksubtopic are not set title:"); Writeln ("Subject:".  $bookSubSubTopic->gettopic ()); Writeln ("title:".  $bookSubSubTopic->gettitle ());  Writeln ("");  Writeln ("End Test responsibility chain mode"); function Writeln ($line _in) {echo $line _in.  Php_eol; }

Results:

Start testing the responsibility chain mode Booktopic set title before: Theme: Magic title: currently no title booktopic after setting title: Theme: Magic title: Harry Potter and the Philosopher's Stone booksubtopic title before: Theme: English Magic title: Harry Potter and the Philosopher's Stone booksubtopic title after set: Theme: English magic title: Harry Potter and the Half-Blood Prince Booksubsubtopic title: The English Modern Magic title: Harry Potter and the Half-Blood Prince Booksubsubtopic, Booksubtopic is not set title: theme: British modern Magic title: Harry Potter and the Philosopher's Stone end test responsibility chain mode