. PHP Design Patterns . PHP Design Patterns Mediator

PHP Design Patterns Mediator

About the Mediator

An object passes all interaction between a number of other objects through itself.

In this example, BookMediator is notified by BookAuthorColleague or BookTitleColleague if they change to all upper case or all lower case. When either changes case, BookMediator calls the other to change it's case to match.

BookMediator.php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved


  include_once('BookColleague.php');
  include_once('BookAuthorColleague.php');
  include_once('BookTitleColleague.php');


  class BookMediator {


    private $authorObject;
    private $titleObject;


    function __construct($author_in, $title_in) {
      $this->authorObject = new BookAuthorColleague($author_in,$this);
      $this->titleObject  = new BookTitleColleague($title_in,$this);
    }


    function getAuthor() {return $this->authorObject;}
    function getTitle() {return $this->titleObject;}


    //when title or author change case, this makes sure the other
	//  stays in sync
    function change(BookColleague $changingClassIn) {
      if ($changingClassIn instanceof BookAuthorColleague) {
        if ('upper' == $changingClassIn->getState()) {
          if ('upper' != $this->getTitle()->getState()) {
            $this->getTitle()->setTitleUpperCase();
          }
        } elseif ('lower' == $changingClassIn->getState()) {
          if ('lower' != $this->getTitle()->getState()) {
            $this->getTitle()->setTitleLowerCase();
          }
        }
      } elseif ($changingClassIn instanceof BookTitleColleague) {
        if ('upper' == $changingClassIn->getState()) {
          if ('upper' != $this->getAuthor()->getState()) {
            $this->getAuthor()->setAuthorUpperCase();
          }
        } elseif ('lower' == $changingClassIn->getState()) {
          if ('lower' != $this->getAuthor()->getState()) {
            $this->getAuthor()->setAuthorLowerCase();
          }
        }
      }
    }


  }

download source, use right-click and "Save Target As..." to save with a .php extension.

BookColleague

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved


  include_once('BookMediator.php');


  abstract class BookColleague {


    private $mediator;


    function __construct($mediator_in) {
      $this->mediator = $mediator_in;
    }


    function getMediator() {return $this->mediator;}


    function changed($changingClassIn) {
      getMediator()->titleChanged($changingClassIn);
    }


  }

download source, use right-click and "Save Target As..." to save with a .php extension.

BookAuthorColleague.php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved


  include_once('BookColleague.php');


  class BookAuthorColleague extends BookColleague {


    private $author;
    private $state;


    function __construct($author_in, $mediator_in) {
      $this->author = $author_in;
      parent::__construct($mediator_in);
    }


    function getAuthor() {return $this->author;}
    function setAuthor($author_in) {$this->author = $author_in;}


    function getState() {return $this->state;}
    function setState($state_in) {$this->state = $state_in;}


    function setAuthorUpperCase() {
      $this->setAuthor(strtoupper($this->getAuthor()));
      $this->setState('upper');
      $this->getMediator()->change($this);
    }


    function setAuthorLowerCase() {
      $this->setAuthor(strtolower($this->getAuthor()));
      $this->setState('lower');
      $this->getMediator()->change($this);
    }


  }

download source, use right-click and "Save Target As..." to save with a .php extension.

BookTitleColleague.php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved


  include_once('BookColleague.php');


  class BookTitleColleague extends BookColleague {


    private $title;
    private $state;


    function __construct($title_in, $mediator_in) {
      $this->title = $title_in;
	  parent::__construct($mediator_in);
    }


    function getTitle() {return $this->title;}
    function setTitle($title_in) {$this->title = $title_in;}


    function getState() {return $this->state;}
    function setState($state_in) {$this->state = $state_in;}


    function setTitleUpperCase() {
      $this->setTitle(strtoupper($this->getTitle()));
      $this->setState('upper');
      $this->getMediator()->change($this);
    }


    function setTitleLowerCase() {
      $this->setTitle(strtolower($this->getTitle()));
      $this->setState('lower');
      $this->getMediator()->change($this);
    }


  }

download source, use right-click and "Save Target As..." to save with a .php extension.

testMediator.php

//copyright Lawrence Truett and FluffyCat.com 2005, all rights reserved


  include_once('BookColleague.php');
  include_once('BookAuthorColleague.php');
  include_once('BookTitleColleague.php');
  include_once('BookMediator.php');


  writeln('BEGIN TESTING MEDIATOR PATTERN');
  writeln('');


  $mediator = new BookMediator('Gamma, Helm, Johnson, and Vlissides',
                               'Design Patterns');
							   
  $author = $mediator->getAuthor();
  $title = $mediator->getTitle();
  
  writeln('Original Author and Title: ');
  writeln('author: ' . $author->getAuthor());
  writeln('title: ' . $title->getTitle());
  writeln('');
  
  $author->setAuthorLowerCase();
  
  writeln('After Author set to Lower Case: ');
  writeln('author: ' . $author->getAuthor());
  writeln('title: ' . $title->getTitle());
  writeln('');


  $title->setTitleUpperCase();
  
  writeln('After Title set to Upper Case: ');
  writeln('author: ' . $author->getAuthor());
  writeln('title: ' . $title->getTitle());
  writeln('');
  
  writeln('END TESTING MEDIATOR PATTERN');


  function writeln($line_in) {
    echo $line_in.'<'.'BR'.'>';
  }

download source, use right-click and "Save Target As..." to save with a .php extension.

output of testMediator.php

BEGIN TESTING MEDIATOR PATTERN


Original Author and Title: 
author: Gamma, Helm, Johnson, and Vlissides
title: Design Patterns


After Author set to Lower Case: 
author: gamma, helm, johnson, and vlissides
title: design patterns


After Title set to Upper Case: 
author: GAMMA, HELM, JOHNSON, AND VLISSIDES
title: DESIGN PATTERNS


END TESTING MEDIATOR PATTERN

References

Design Patterns

Design Patterns by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides

PHP 5

The Official PHP web site
Core PHP Programming, 3rd Edition by Leon Atkinson and Zeev Suraski

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