PHP7 Adapter

Author: Dominik Liebler

Structural/Adapter/Book.php

@@ -2,22 +2,25 @@
 
 namespace DesignPatterns\Structural\Adapter;
 
-/**
- * Book is a concrete and standard paper book.
- */
-class Book implements PaperBookInterface
+class Book implements BookInterface
 {
     /**
-     * {@inheritdoc}
+     * @var int
      */
+    private $page;
+
     public function open()
     {
+        $this->page = 1;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function turnPage()
     {
+        $this->page++;
+    }
+
+    public function getPage(): int
+    {
+        return $this->page;
     }
 }

Structural/Adapter/BookInterface.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace DesignPatterns\Structural\Adapter;
+
+interface BookInterface
+{
+    public function turnPage();
+
+    public function open();
+
+    public function getPage(): int;
+}

Structural/Adapter/EBookAdapter.php

@@ -3,41 +3,45 @@
 namespace DesignPatterns\Structural\Adapter;
 
 /**
- * EBookAdapter is an adapter to fit an e-book like a paper book.
- *
- * This is the adapter here. Notice it implements PaperBookInterface,
- * therefore you don't have to change the code of the client which using paper book.
+ * This is the adapter here. Notice it implements BookInterface,
+ * therefore you don't have to change the code of the client which is using a Book
  */
-class EBookAdapter implements PaperBookInterface
+class EBookAdapter implements BookInterface
 {
     /**
      * @var EBookInterface
      */
     protected $eBook;
 
     /**
-     * Notice the constructor, it "wraps" an electronic book.
-     *
-     * @param EBookInterface $ebook
+     * @param EBookInterface $eBook
      */
-    public function __construct(EBookInterface $ebook)
+    public function __construct(EBookInterface $eBook)
     {
-        $this->eBook = $ebook;
+        $this->eBook = $eBook;
     }
 
     /**
      * This class makes the proper translation from one interface to another.
      */
     public function open()
     {
-        $this->eBook->pressStart();
+        $this->eBook->unlock();
     }
 
-    /**
-     * turns pages.
-     */
     public function turnPage()
     {
         $this->eBook->pressNext();
     }
+
+    /**
+     * notice the adapted behavior here: EBookInterface::getPage() will return two integers, but BookInterface
+     * supports only a current page getter, so we adapt the behavior here
+     *
+     * @return int
+     */
+    public function getPage(): int
+    {
+        return $this->eBook->getPage()[0];
+    }
 }

Structural/Adapter/EBookInterface.php

@@ -2,22 +2,16 @@
 
 namespace DesignPatterns\Structural\Adapter;
 
-/**
- * EBookInterface is a contract for an electronic book.
- */
 interface EBookInterface
 {
-    /**
-     * go to next page.
-     *
-     * @return mixed
-     */
+    public function unlock();
+
     public function pressNext();
 
     /**
-     * start the book.
+     * returns current page and total number of pages, like [10, 100] is page 10 of 100
      *
-     * @return mixed
+     * @return int[]
      */
-    public function pressStart();
+    public function getPage(): array;
 }

Structural/Adapter/Kindle.php

@@ -3,21 +3,37 @@
 namespace DesignPatterns\Structural\Adapter;
 
 /**
- * Kindle is a concrete electronic book.
+ * this is the adapted class. In production code, this could be a class from another package, some vendor code.
+ * Notice that it uses another naming scheme and the implementation does something similar but in another way
  */
 class Kindle implements EBookInterface
 {
     /**
-     * {@inheritdoc}
+     * @var int
      */
+    private $page = 1;
+
+    /**
+     * @var int
+     */
+    private $totalPages = 100;
+
     public function pressNext()
+    {
+        $this->page++;
+    }
+
+    public function unlock()
     {
     }
 
     /**
-     * {@inheritdoc}
+     * returns current page and total number of pages, like [10, 100] is page 10 of 100
+     *
+     * @return int[]
      */
-    public function pressStart()
+    public function getPage(): array
     {
+        return [$this->page, $this->totalPages];
     }
 }

Structural/Adapter/PaperBookInterface.php

@@ -28,7 +28,7 @@ Code
 
 You can also find these code on `GitHub`_
 
-PaperBookInterface.php
+BookInterface.php
 
 .. literalinclude:: PaperBookInterface.php
    :language: php

Structural/Adapter/README.rst

@@ -5,37 +5,26 @@
 use DesignPatterns\Structural\Adapter\Book;
 use DesignPatterns\Structural\Adapter\EBookAdapter;
 use DesignPatterns\Structural\Adapter\Kindle;
-use DesignPatterns\Structural\Adapter\PaperBookInterface;
 
-/**
- * AdapterTest shows the use of an adapted e-book that behave like a book
- * You don't have to change the code of your client.
- */
 class AdapterTest extends \PHPUnit_Framework_TestCase
 {
-    /**
-     * @return array
-     */
-    public function getBook()
+    public function testCanTurnPageOnBook()
     {
-        return array(
-            array(new Book()),
-            // we build a "wrapped" electronic book in the adapter
-            array(new EBookAdapter(new Kindle())),
-        );
+        $book = new Book();
+        $book->open();
+        $book->turnPage();
+
+        $this->assertEquals(2, $book->getPage());
     }
 
-    /**
-     * This client only knows paper book but surprise, surprise, the second book
-     * is in fact an electronic book, but both work the same way.
-     *
-     * @param PaperBookInterface $book
-     *
-     * @dataProvider getBook
-     */
-    public function testIAmAnOldClient(PaperBookInterface $book)
+    public function testCanTurnPageOnKindleLikeInANormalBook()
     {
-        $this->assertTrue(method_exists($book, 'open'));
-        $this->assertTrue(method_exists($book, 'turnPage'));
+        $kindle = new Kindle();
+        $book = new EBookAdapter($kindle);
+
+        $book->open();
+        $book->turnPage();
+
+        $this->assertEquals(2, $book->getPage());
     }
 }