Sample of PHP: Design Patterns Adapter

About the Adapter

In the Adapter Design Pattern, a class converts the interface of one class to be what another class expects.

In this example we have a SimpleBook class that has a getAuthor() and getTitle() methods. The client, testAdapter.php, expects a getAuthorAndTitle() method. To “adapt” SimpleBook for testAdapter we have an adapter class, BookAdapter, which takes in an instance of SimpleBook, and uses the SimpleBook getAuthor() and getTitle() methods in it’s own getAuthorAndTitle() method.

Adapters are helpful if you want to use a class that doesn’t have quite the exact methods you need, and you can’t change the orignal class. The adapter can take the methods you can access in the original class, and adapt them into the methods you need.

SimpleBook.php

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

  class SimpleBook {

    private $author;
    private $title;

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

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

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

  }
download source, use right-click and “Save Target As…” to save with a .php extension.

BookAdapter.php

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

  include_once('SimpleBook.php');

  class BookAdapter {

    private $book;

    function __construct(SimpleBook $book_in) {
      $this->book = $book_in;
    }

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

  }
download source, use right-click and “Save Target As…” to save with a .php extension.

testAdapter.php

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

  include_once('SimpleBook.php');
  include_once('BookAdapter.php');

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

  echo 'BEGIN TESTING ADAPTER PATTERN'.BR;
  echo BR;

  $book = new SimpleBook("Gamma, Helm, Johnson, and Vlissides",
                         "Design Patterns");

  $bookAdapter = new BookAdapter($book);

  echo 'Author and Title: '.$bookAdapter->getAuthorAndTitle();

  echo BR.BR;
  echo 'END TESTING ADAPTER PATTERN'.BR;
download source, use right-click and “Save Target As…” to save with a .php extension.

output of testAdapter.php

BEGIN TESTING ADAPTER PATTERN

Author and Title: Design Patterns by Gamma, Helm, Johnson, and Vlissides

END TESTING ADAPTER PATTERN