. PHP Design Patterns . PHP Design Patterns Template

PHP Design Patterns Template

About the Template

In the Template Pattern an abstract class will define a method with an algorithm, and methods which the algorithm will use. The methods the algorithm uses can be either required or optional. The optional method should by default do nothing.

The Template Pattern is unusual in that the Parent class has a lot of control.

In this example, the TemplateAbstract class has the showBookTitleInfo() method, which will call the methods getTitle() and getAuthor(). The method getTitle() must be overridden, while the method getAuthor() is not required.

TemplateAbstract.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved

  include_once('Book.php');  
  
  abstract class TemplateAbstract {
    
    //the template method 
    //  sets up a general algorithm for the whole class 
    public final function showBookTitleInfo($book_in) {
      $title = $book_in->getTitle();
      $author = $book_in->getAuthor();
      $processedTitle = $this->processTitle($title);
      $processedAuthor = $this->processAuthor($author);
      if (NULL == $processedAuthor) {
        $processed_info = $processedTitle;
      } else {
        $processed_info = $processedTitle.' by '.$processedAuthor;
      }
      return $processed_info;
    }
    
    //the primitive operation
    //  this function must be overridded
    abstract function processTitle($title);
    
    //the hook operation
    //  this function may be overridden, 
    //  but does nothing if it is not
    function processAuthor($author) {
      return NULL;
    } 
    
  }

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TemplateExclaim.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved

  include_once('TemplateAbstract.php');  
  
  class TemplateExclaim extends TemplateAbstract {
    
    function processTitle($title) {
      return Str_replace(' ','!!!',$title); 
    }
    
    function processAuthor($author) {
      return Str_replace(' ','!!!',$author);
    }
  }

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TemplateStars.php

//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved

  include_once('TemplateAbstract.php');  
  
  class TemplateStars extends TemplateAbstract {
    
    function processTitle($title) {
      return Str_replace(' ','*',$title); 
    }
  }

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Book.php


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

    private $author;
    private $title;

    function __construct($title_in, $author_in) {
      $this->author = $author_in;
      $this->title  = $title_in;
    }

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

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

    function getAuthorAndTitle() {
      return $this->getTitle() . ' by ' . $this->getAuthor();
    }

  }

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testTemplate.php


//copyright Lawrence Truett and FluffyCat.com 2006, all rights reserved

  include_once('Book.php');
  include_once('TemplateExclaim.php');
  include_once('TemplateStars.php');

  define('BR', '<'.'BR'.'>');

  echo 'BEGIN TESTING TEMPLATE PATTERN'.BR;
  echo BR;
  
  $book = new Book('PHP for Cats','Larry Truett');
  
  $exclaimTemplate = new TemplateExclaim();  
  $starsTemplate = new TemplateStars();
  
  echo 'test 1 - show exclaim template'.BR;
  echo $exclaimTemplate->showBookTitleInfo($book);
  echo BR.BR;

  echo 'test 2 - show stars template'.BR;
  echo $starsTemplate->showBookTitleInfo($book);
  echo BR.BR; 

  echo 'END TESTING TEMPLATE PATTERN'.BR;

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output of testTemplate.php

BEGIN TESTING TEMPLATE PATTERN


test 1 - show exclaim template
PHP!!!for!!!Cats by Larry!!!Truett


test 2 - show stars template
PHP*for*Cats


END TESTING TEMPLATE 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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