目的
讓物件變得可迭代并表現得像物件集合，
例子
- 在檔案中的所有行（物件表示形式的）上逐行處理檔案（也是物件）
PHP 標準庫 (SPL) 定義了一個最適合此模式的介面迭代器！往往也需要實作 Countable 介面，允許在迭代器物件上使用 count($object) 方法，
UML圖
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代碼
- Book.php
<?php
namespace DesignPatterns\Behavioral\Iterator;
class Book
{
/**
* @var string
*/
private $author;
/**
* @var string
*/
private $title;
public function __construct(string $title, string $author)
{
$this->author = $author;
$this->title = $title;
}
public function getAuthor(): string
{
return $this->author;
}
public function getTitle(): string
{
return $this->title;
}
public function getAuthorAndTitle(): string
{
return $this->getTitle().' by '.$this->getAuthor();
}
}
- BookList.php
<?php
namespace DesignPatterns\Behavioral\Iterator;
class BookList implements \Countable, \Iterator
{
/**
* @var Book[]
*/
private $books = [];
/**
* @var int
*/
private $currentIndex = 0;
public function addBook(Book $book)
{
$this->books[] = $book;
}
public function removeBook(Book $bookToRemove)
{
foreach ($this->books as $key => $book) {
if ($book->getAuthorAndTitle() === $bookToRemove->getAuthorAndTitle()) {
unset($this->books[$key]);
}
}
$this->books = array_values($this->books);
}
public function count(): int
{
return count($this->books);
}
public function current(): Book
{
return $this->books[$this->currentIndex];
}
public function key(): int
{
return $this->currentIndex;
}
public function next()
{
$this->currentIndex++;
}
public function rewind()
{
$this->currentIndex = 0;
}
public function valid(): bool
{
return isset($this->books[$this->currentIndex]);
}
}
測驗
- Tests/IteratorTest.php
<?php
namespace DesignPatterns\Behavioral\Iterator\Tests;
use DesignPatterns\Behavioral\Iterator\Book;
use DesignPatterns\Behavioral\Iterator\BookList;
use DesignPatterns\Behavioral\Iterator\BookListIterator;
use DesignPatterns\Behavioral\Iterator\BookListReverseIterator;
use PHPUnit\Framework\TestCase;
class IteratorTest extends TestCase
{
public function testCanIterateOverBookList()
{
$bookList = new BookList();
$bookList->addBook(new Book('Learning PHP Design Patterns', 'William Sanders'));
$bookList->addBook(new Book('Professional Php Design Patterns', 'Aaron Saray'));
$bookList->addBook(new Book('Clean Code', 'Robert C. Martin'));
$books = [];
foreach ($bookList as $book) {
$books[] = $book->getAuthorAndTitle();
}
$this->assertEquals(
[
'Learning PHP Design Patterns by William Sanders',
'Professional Php Design Patterns by Aaron Saray',
'Clean Code by Robert C. Martin',
],
$books
);
}
public function testCanIterateOverBookListAfterRemovingBook()
{
$book = new Book('Clean Code', 'Robert C. Martin');
$book2 = new Book('Professional Php Design Patterns', 'Aaron Saray');
$bookList = new BookList();
$bookList->addBook($book);
$bookList->addBook($book2);
$bookList->removeBook($book);
$books = [];
foreach ($bookList as $book) {
$books[] = $book->getAuthorAndTitle();
}
$this->assertEquals(
['Professional Php Design Patterns by Aaron Saray'],
$books
);
}
public function testCanAddBookToList()
{
$book = new Book('Clean Code', 'Robert C. Martin');
$bookList = new BookList();
$bookList->addBook($book);
$this->assertCount(1, $bookList);
}
public function testCanRemoveBookFromList()
{
$book = new Book('Clean Code', 'Robert C. Martin');
$bookList = new BookList();
$bookList->addBook($book);
$bookList->removeBook($book);
$this->assertCount(0, $bookList);
}
}
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