疊代器模式，提供一種方法來簡單控制一個集合物件，這段過程並不會暴露該物件的來源或修改它，就有點像是你的背包(Bag)一樣，疊代器(Iterator)可以簡單控制你背包中的大頭菜(Turnips)以及鈴錢(Bells)。
首先我們一樣要先建立大頭菜物件(Turnips)，並且賦予一些簡單方法，像是島嶼(Island)、鈴錢價格(Price)及數量(Count)，並且提供簡單的取得(get)及賦予(set)方法。
Turnips.php
/**
* Class Turnips.
*/
class Turnips
{
/**
* @var string
*/
protected string $island;
/**
* @var int
*/
protected int $price;
/**
* @var int
*/
protected int $count;
/**
* Turnips constructor.
*
* @param string $island
* @param int $price
* @param int $count
*/
public function __construct(string $island, int $price, int $count)
{
$this->setIsland($island);
$this->setPrice($price);
$this->setCount($count);
}
/**
* @param string $island
*/
public function setIsland(string $island)
{
$this->island = $island;
}
/**
* @param int $price
*/
public function setPrice(int $price)
{
$this->price = $price;
}
/**
* @param int $count
*/
public function setCount(int $count)
{
$this->count = $count;
}
/**
* @return string
*/
public function getIsland(): string
{
return $this->island;
}
/**
* @return int
*/
public function getPrice(): int
{
return $this->price;
}
/**
* @return int
*/
public function getCount(): int
{
return $this->count;
}
/**
* @return int
*/
public function calculatePrice(): int
{
return $this->getPrice() * $this->getCount();
}
}再來我們要建立背包(Bag)來負責管理大頭菜這個集合，這裡比較特別的是我們要實作 Countable 以及 Iterator 這兩個介面，讓背包可以直接提供 Count 方法、陣列 Array 相關方法。
Bag.php
use Countable;
use Iterator;
/**
* Class Bag.
*/
class Bag implements Countable, Iterator
{
/**
* @var Turnips[]
*/
protected array $turnips = [];
/**
* @var int
*/
protected int $currentIndex = 0;
/**
* @param Turnips
*/
public function addTurnips(Turnips $turnips)
{
$this->turnips[] = $turnips;
}
/**
* @param Turnips
*/
public function removeTurnips(Turnips $turnipsToRemove)
{
foreach ($this->turnips as $key => $turnip) {
if ($turnip->getIsland() === $turnipsToRemove->getIsland()) {
unset($this->turnips[$key]);
}
}
$this->turnips = array_values($this->turnips);
}
/**
* @return int
*/
public function count(): int
{
return count($this->turnips);
}
/**
* @return Turnips
*/
public function current(): Turnips
{
return $this->turnips[$this->currentIndex];
}
/**
* @return int
*/
public function key(): int
{
return $this->currentIndex;
}
/**
* @return void
*/
public function next()
{
$this->currentIndex++;
}
/**
* @return void
*/
public function rewind()
{
$this->currentIndex = 0;
}
/**
* @return bool
*/
public function valid(): bool
{
return isset($this->turnips[$this->currentIndex]);
}
}繼承 Countable 這個類別可以使用 count() 這個方法，因此需要實作它。
Countable {
/* Methods */
abstract public count ( void ) : int
}繼承 Iterator 這個類別可以使用 current()、key()、next()、rewind()、valid() 這些方法，因此需要實作它們。
Iterator extends Traversable {
/* Methods */
abstract public current ( void ) : mixed
abstract public key ( void ) : scalar
abstract public next ( void ) : void
abstract public rewind ( void ) : void
abstract public valid ( void ) : bool
}IteratorPatternTest.php
/**
* Class IteratorPatternTest.
*/
class IteratorPatternTest extends TestCase
{
/**
* @test
*/
public function test_can_iterate_over_bag()
{
$bag = new Bag();
$bag->addTurnips(new Turnips('Island_A', 100, 40));
$bag->addTurnips(new Turnips('Island_B', 90, 40));
$bag->addTurnips(new Turnips('Island_C', 80, 40));
$islands = [];
foreach ($bag as $turnips) {
$islands[] = $turnips->getIsland();
}
$this->assertSame(
array(
'Island_A',
'Island_B',
'Island_C'
),
$islands
);
}
/**
* @test
*/
public function test_can_iterate_over_bag_after_removing_turnips()
{
$turnipsA = new Turnips('Island_A', 100, 40);
$turnipsB = new Turnips('Island_B', 200, 10);
$bag = new Bag();
$bag->addTurnips($turnipsA);
$bag->addTurnips($turnipsB);
$bag->removeTurnips($turnipsA);
$islands = [];
foreach ($bag as $turnips) {
$islands[] = $turnips->getIsland();
}
$this->assertSame(
array('Island_B'),
$islands
);
}
/**
* @test
*/
public function test_can_add_turnips_to_bag()
{
$turnips = new Turnips('Island_A', 100, 40);
$bag = new Bag();
$bag->addTurnips($turnips);
$this->assertCount(1, $bag);
}
/**
* @test
*/
public function test_can_remove_turnips_from_bag()
{
$turnips = new Turnips('Island_A', 100, 40);
$bag = new Bag();
$bag->addTurnips($turnips);
$bag->removeTurnips($turnips);
$this->assertCount(0, $bag);
}
}最後測試的執行結果會獲得如下：
PHPUnit Pretty Result Printer 0.28.0 by Codedungeon and contributors.
==> Configuration: ~/php-design-pattern/vendor/codedungeon/phpunit-result-printer/src/phpunit-printer.yml
PHPUnit 9.2.6 by Sebastian Bergmann and contributors.
==> ...fResponsibilitiesTest ✔ ✔ ✔
==> CommandPatternTest ✔
==> IteratorPatternTest ✔ ✔ ✔ ✔
==> AbstractFactoryTest ✔ ✔ ✔ ✔
==> BuilderPatternTest ✔ ✔ ✔ ✔
==> FactoryMethodTest ✔ ✔ ✔ ✔
==> PoolPatternTest ✔ ✔
==> PrototypePatternTest ✔ ✔
==> SimpleFactoryTest ✔ ✔ ✔ ✔
==> SingletonPatternTest ✔
==> StaticFactoryTest ✔ ✔ ✔ ✔ ✔
==> AdapterPatternTest ✔ ✔
==> BridgePatternTest ✔ ✔ ✔
==> CompositePatternTest ✔ ✔ ✔
==> DataMapperTest ✔ ✔
==> DecoratorPatternTest ✔ ✔
==> DependencyInjectionTest ✔ ✔ ✔
==> FacadePatternTest ✔
==> FluentInterfaceTest ✔
==> FlyweightPatternTest ✔
==> ProxyPatternTest ✔ ✔
==> RegistryPatternTest ✔ ✔ ✔ ✔ ✔
Time: 00:00.117, Memory: 6.00 MB
OK (59 tests, 126 assertions)