享元模式，在定義上來說是共享物件，將相似的物件集中整理，減少記憶體上的使用，舉例來說每座島的大頭菜鈴錢價格都不同，有些朋友會送你大頭菜，但因為朋友太多了，所以需要有個地方集中放這些大頭菜，並且記錄起來，每個朋友都送你一組大頭彩，但你不能重複紀錄，不然你只收到一組大頭菜，帳上卻紀錄兩組，這樣就不好了。
首先我們須要先定義大頭菜作為共享目標，紀錄了島嶼、鈴錢以及數量，並且提供了簡單的計算總價方法。
FlyweightInterface.php
/**
* Interface FlyweightInterface.
*/
interface FlyweightInterface
{
/**
* @return int
*/
public function calculatePrice(): int;
}/**
* Class TurnipsFlyweight.
*/
class TurnipsFlyweight implements FlyweightInterface
{
/**
* @var string
*/
protected $island;
/**
* @var int
*/
protected $price;
/**
* @var int
*/
protected $count;
/**
* @param string $island
* @param int $price
* @param int $count
*/
public function __construct(string $island, int $price, int $count)
{
$this->island = $island;
$this->price = $price;
$this->count = $count;
}
/**
* @return int
*/
public function calculatePrice(): int
{
return $this->price * $this->count;
}
}再來製作享元工廠，主要負責建立、管理大頭菜共享物件，以及提供基本功能，例如計算全部大頭菜總鈴錢的方法。
FlyweightFactory.php
use Countable;
/**
* Class FlyweightFactory.
*/
class FlyweightFactory implements Countable
{
/**
* @var TurnipsFlyweight[]
*/
protected $turnips = [];
/**
* @param string $island
* @param int $price
* @param int $count
*/
public function get(string $island, int $price = 0, int $count = 0): TurnipsFlyweight
{
if (!isset($this->turnips[$island])) {
$this->turnips[$island] = new TurnipsFlyweight($island, $price, $count);
}
return $this->turnips[$island];
}
/**
* @return int
*/
public function calculateTotal(): int
{
$total = 0;
foreach ($this->turnips as $turnip) {
$total += $turnip->calculatePrice();
}
return $total;
}
/**
* @return int
*/
public function count(): int
{
return count($this->turnips);
}
}繼承 Countable 這個類別可以使用 count() 這個方法，因此需要實作它。
class Countable {
/* Methods */
abstract public count ( void ) : int
}最後我們要對享元物件、工廠進行簡單的測試，假設我們已經擁有了許多大頭菜，那麼我們有幾個需要做的檢查事項：
- 依序塞入享元，並且計算該次塞入的大頭菜跟紀錄所算出來的鈴錢是否相符。
- 大頭菜全部塞入後，所存入的筆數是否跟實際上相符。
- 最後計算所有大頭菜的總鈴錢是否是正確的。
FlyweightPatternTest.php
/**
* Class FlyweightPatternTest.
*/
class FlyweightPatternTest extends TestCase
{
/**
* @var array
*/
protected $turnips = array(
'Island_A' => array('price' => 90, 'count' => 40),
'Island_B' => array('price' => 92, 'count' => 36),
'Island_C' => array('price' => 94, 'count' => 32),
'Island_D' => array('price' => 96, 'count' => 28),
'Island_E' => array('price' => 98, 'count' => 24),
'Island_F' => array('price' => 100, 'count' => 20),
'Island_G' => array('price' => 102, 'count' => 16),
'Island_H' => array('price' => 104, 'count' => 12),
'Island_I' => array('price' => 106, 'count' => 8),
'Island_J' => array('price' => 108, 'count' => 4),
'Island_K' => array('price' => 110, 'count' => 40),
);
/**
* @test
*/
public function test_flyweight()
{
$factory = new FlyweightFactory();
foreach ($this->turnips as $key => $value) {
$flyweight = $factory->get($key, $value['price'], $value['count']);
$total = $flyweight->calculatePrice();
$this->assertEquals($value['price'] * $value['count'], $total);
}
$this->assertCount(count($this->turnips), $factory);
$this->assertEquals(25520, $factory->calculateTotal());
}
}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.
==> AbstractFactoryTest ✔ ✔ ✔ ✔
==> BuilderPatternTest ✔ ✔ ✔ ✔
==> FactoryMethodTest ✔ ✔ ✔ ✔
==> PoolPatternTest ✔ ✔
==> PrototypePatternTest ✔ ✔
==> SimpleFactoryTest ✔ ✔ ✔ ✔
==> SingletonPatternTest ✔
==> StaticFactoryTest ✔ ✔ ✔ ✔ ✔
==> AdapterPatternTest ✔ ✔
==> BridgePatternTest ✔ ✔ ✔
==> CompositePatternTest ✔ ✔ ✔
==> DataMapperTest ✔ ✔
==> DecoratorPatternTest ✔ ✔
==> DependencyInjectionTest ✔ ✔ ✔
==> FacadePatternTest ✔
==> FluentInterfaceTest ✔
==> FlyweightPatternTest ✔
Time: 00:00.030, Memory: 6.00 MB
OK (44 tests, 107 assertions)