PHP デザイン パターン シリーズ -- イテレータ パターン (イテレータ)

1. モード定義

イテレーター モード (Iterator)、カーソル (Cursor) モードとも呼ばれます。オブジェクトの内部詳細を公開せずに、コンテナ オブジェクト内の個々の要素にアクセスする方法を提供します。

集約オブジェクトにアクセスする必要があり、オブジェクトがどのようなものであってもそれを走査する必要がある場合は、反復子パターンの使用を検討する必要があります。さらに、複数の方法でコレクションを走査する必要がある場合は、反復子パターンの使用を検討できます。イテレータ パターンは、開始、次、終了するかどうか、現在の項目など、さまざまなコレクション構造をトラバースするための統一インターフェイスを提供します。

PHP 標準ライブラリ (SPL) は、反復子インターフェイス Iterator を提供します。反復子パターンを実装するには、このインターフェイスを実装するだけです。

2. UML クラス図

3. サンプルコード

Book.php

<?phpnamespace DesignPatterns\Behavioral\Iterator;class Book{    private $author;    private $title;    public function __construct($title, $author)    {        $this->author = $author;        $this->title = $title;    }    public function getAuthor()    {        return $this->author;    }    public function getTitle()    {        return $this->title;    }    public function getAuthorAndTitle()    {        return $this->getTitle() . ' by ' . $this->getAuthor();    }}

BookList.php

<?phpnamespace DesignPatterns\Behavioral\Iterator;class BookList implements \Countable{    private $books;    public function getBook($bookNumberToGet)    {        if (isset($this->books[$bookNumberToGet])) {            return $this->books[$bookNumberToGet];        }        return null;    }    public function addBook(Book $book)    {        $this->books[] = $book;    }    public function removeBook(Book $bookToRemove)    {        foreach ($this->books as $key => $book) {            /** @var Book $book */            if ($book->getAuthorAndTitle() === $bookToRemove->getAuthorAndTitle()) {                unset($this->books[$key]);            }        }    }    public function count()    {        return count($this->books);    }}

BookListIterator.php

<?phpnamespace DesignPatterns\Behavioral\Iterator;class BookListIterator implements \Iterator{    /**     * @var BookList     */    private $bookList;    /**     * @var int     */    protected $currentBook = 0;    public function __construct(BookList $bookList)    {        $this->bookList = $bookList;    }    /**     * Return the current book     * @link http://php.net/manual/en/iterator.current.php     * @return Book Can return any type.     */    public function current()    {        return $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Move forward to next element     * @link http://php.net/manual/en/iterator.next.php     * @return void Any returned value is ignored.     */    public function next()    {        $this->currentBook++;    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Return the key of the current element     * @link http://php.net/manual/en/iterator.key.php     * @return mixed scalar on success, or null on failure.     */    public function key()    {        return $this->currentBook;    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Checks if current position is valid     * @link http://php.net/manual/en/iterator.valid.php     * @return boolean The return value will be casted to boolean and then evaluated.     *       Returns true on success or false on failure.     */    public function valid()    {        return null !== $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Rewind the Iterator to the first element     * @link http://php.net/manual/en/iterator.rewind.php     * @return void Any returned value is ignored.     */    public function rewind()    {        $this->currentBook = 0;    }}

BookListReverseIterator.php

<?phpnamespace DesignPatterns\Behavioral\Iterator;class BookListReverseIterator implements \Iterator{    /**     * @var BookList     */    private $bookList;    /**     * @var int     */    protected $currentBook = 0;    public function __construct(BookList $bookList)    {        $this->bookList = $bookList;        $this->currentBook = $this->bookList->count() - 1;    }    /**     * Return the current book     * @link http://php.net/manual/en/iterator.current.php     * @return Book Can return any type.     */    public function current()    {        return $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Move forward to next element     * @link http://php.net/manual/en/iterator.next.php     * @return void Any returned value is ignored.     */    public function next()    {        $this->currentBook--;    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Return the key of the current element     * @link http://php.net/manual/en/iterator.key.php     * @return mixed scalar on success, or null on failure.     */    public function key()    {        return $this->currentBook;    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Checks if current position is valid     * @link http://php.net/manual/en/iterator.valid.php     * @return boolean The return value will be casted to boolean and then evaluated.     *       Returns true on success or false on failure.     */    public function valid()    {        return null !== $this->bookList->getBook($this->currentBook);    }    /**     * (PHP 5 >= 5.0.0)<br/>     * Rewind the Iterator to the first element     * @link http://php.net/manual/en/iterator.rewind.php     * @return void Any returned value is ignored.     */    public function rewind()    {        $this->currentBook = $this->bookList->count() - 1;    }}

4. テストコード

Tests/IteratorTest.php

<?phpnamespace DesignPatterns\Behavioral\Iterator\Tests;use DesignPatterns\Behavioral\Iterator\Book;use DesignPatterns\Behavioral\Iterator\BookList;use DesignPatterns\Behavioral\Iterator\BookListIterator;use DesignPatterns\Behavioral\Iterator\BookListReverseIterator;class IteratorTest extends \PHPUnit_Framework_TestCase{    /**     * @var BookList     */    protected $bookList;    protected function setUp()    {        $this->bookList = new BookList();        $this->bookList->addBook(new Book('Learning PHP Design Patterns', 'William Sanders'));        $this->bookList->addBook(new Book('Professional Php Design Patterns', 'Aaron Saray'));        $this->bookList->addBook(new Book('Clean Code', 'Robert C. Martin'));    }    public function expectedAuthors()    {        return array(            array(                array(                    'Learning PHP Design Patterns by William Sanders',                    'Professional Php Design Patterns by Aaron Saray',                    'Clean Code by Robert C. Martin'                )            ),        );    }    /**     * @dataProvider expectedAuthors     */    public function testUseAIteratorAndValidateAuthors($expected)    {        $iterator = new BookListIterator($this->bookList);        while ($iterator->valid()) {            $expectedBook = array_shift($expected);            $this->assertEquals($expectedBook, $iterator->current()->getAuthorAndTitle());            $iterator->next();        }    }    /**     * @dataProvider expectedAuthors     */    public function testUseAReverseIteratorAndValidateAuthors($expected)    {        $iterator = new BookListReverseIterator($this->bookList);        while ($iterator->valid()) {            $expectedBook = array_pop($expected);            $this->assertEquals($expectedBook, $iterator->current()->getAuthorAndTitle());            $iterator->next();        }    }    /**     * Test BookList Remove     */    public function testBookRemove()    {        $this->bookList->removeBook($this->bookList->getBook(0));        $this->assertEquals($this->bookList->count(), 2);    }}