修飾模式，或者稱裝飾者模式，為物件動態增加新的方法，就想像你最初的大頭菜沒有想過他會壞掉，某天突然覺得讓大頭菜壞掉好像很好玩，但你不能把整個大頭菜砍掉重練，所以你希望可以不改變既有的大頭菜，在大頭菜額外再套上新的功能，那就是壞掉。
首先我們會需要定義出最初始大頭菜的介面，以及其最初的功能。
TurnipsInterface.php
/**
* Interface TurnipsInterface.
*/
interface TurnipsInterface
{
public function calculatePrice(): int;
}TurnipsService.php
/**
* Class TurnipsService.
*/
class TurnipsService implements TurnipsInterface
{
/**
* @var int
*/
protected $price;
/**
* @var int
*/
protected $count;
/**
* TurnipsService constructor.
*
* @param int $price
* @param int $count
*/
public function __construct(int $price, int $count)
{
$this->price = $price;
$this->count = $count;
}
/**
* @return int
*/
public function calculatePrice(): int
{
return $this->price * $this->count;
}
}再來我們需要建立裝飾器(Decorator)，來修飾我們後來添加的壞掉功能，並且把最初始的大頭菜丟進去，讓大頭菜直接壞掉，沒有壞掉就拿石頭丟他！
TurnipsDecorator.php
/**
* Class TurnipsDecorator.
*/
abstract class TurnipsDecorator implements TurnipsInterface
{
/**
* @var TurnipsInterface
*/
protected $turnips;
/**
* TurnipsDecorator constructor.
*
* @param TurnipsInterface $turnips
*/
public function __construct(TurnipsInterface $turnips)
{
$this->turnips = $turnips;
}
}Turnips.php
/**
* Class Turnips.
*/
class Turnips extends TurnipsDecorator
{
/**
* @return int
*/
public function calculatePrice(): int
{
return $this->turnips->calculatePrice();
}
}Spoiled.php
/**
* Class Spoiled.
*/
class Spoiled extends TurnipsDecorator
{
/**
* @return int
*/
public function calculatePrice(): int
{
return 0;
}
}完成了大頭菜裝飾器之後，我們接下來要驗證前面所寫的裝飾器是否能夠正常運行，因此我們有幾個重要項目要來做測試：
- 測試正常的大頭菜是否可以賣鈴錢。
- 測試壞掉的大頭菜是否沒辦法賣鈴錢。
/**
* Class DecoratorPatternTest.
*/
class DecoratorPatternTest extends TestCase
{
/**
* 測試正常的大頭菜是否可以賣鈴錢。
*
* @test
*/
public function test_turnips()
{
$service = new TurnipsService(100, 40);
$turnips = new Turnips($service);
$this->assertEquals(4000, $turnips->calculatePrice());
}
/**
* 測試壞掉的大頭菜是否沒辦法賣鈴錢。
*
* @test
*/
public function test_spoiled()
{
$service = new TurnipsService(100, 40);
$turnips = new Spoiled($service);
$this->assertEquals(0, $turnips->calculatePrice());
}
}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 ✔ ✔
Time: 00:00.050, Memory: 6.00 MB
OK (41 tests, 88 assertions)