規格模式,將邏輯條件給抽離出來,獨立成一個模組,而不是在物件內透過邏輯判斷來撰寫複雜的程式碼,簡化物件所需要實踐的邏輯,物件可以套用一個規則,也可以套用多種規則,就像大頭菜本身的價格運算是一種規格,過期後的價格運算又是另一種規格,可以把這個價格運算的邏輯抽離出來獨立成模組。
首當其中我們需要把大頭菜物件給建立出來,具有價格(price)以及數量(count)的記錄、讀取功能,原本會提供計算鈴錢總計(calculatePrice)的功能,但這部分是運算邏輯,所以我們需要把這個功能抽離出來放到規格模組(Specification)當中。
Turnips.php
/**
* Class Turnips.
*/
class Turnips
{
/**
* @var int
*/
protected int $price = 0;
/**
* @var int
*/
protected int $count = 0;
/**
* Turnips constructor.
*
* @param int $price
* @param int $count
*/
public function __construct(int $price, int $count)
{
$this->price = $price;
$this->count = $count;
}
/**
* @return int
*/
public function getPrice(): int
{
return $this->price;
}
/**
* @return int
*/
public function getCount(): int
{
return $this->count;
}
}
再來定義規格模組(Specification)的介面,這個介面會需要實作大頭菜尚未補足的邏輯,也就是計算鈴錢價格(calculatePrice)的這項功能。
Specification.php
/**
* Interface Specification.
*/
interface Specification
{
/**
* @return int
*/
public function calculatePrice(): int;
}
最後我們有兩種規格模式,分別是正常的大頭菜、壞掉的大頭菜,我們先來實作正常的情況下,大頭菜的總計鈴錢計算規格,這裡提供了可以丟大頭菜集合的方式,無論你有多少顆大頭菜,你通通都丟過來,我會全部加總一起算,就算是一顆也沒問題。
TurnipsSpecification.php
/**
* Class TurnipsSpecification.
*/
class TurnipsSpecification implements Specification
{
/**
* @var Turnips[]
*/
protected array $turnips;
/**
* Turnips constructor.
*
* @param Turnips[] $turnips
*/
public function __construct(Turnips ...$turnips)
{
$this->turnips = $turnips;
}
/**
* @return int
*/
public function calculatePrice(): int
{
$total = 0;
foreach ($this->turnips as $turnip) {
$total += $turnip->getPrice() * $turnip->getCount();
}
return $total;
}
}
最後是實作壞掉的大頭菜計算模式,這裡也是一樣提供一顆或多顆大頭菜計算,不一樣的點在於因為是壞掉的大頭菜,無法賣出鈴錢,所以無論你丟過來幾顆,我都會回傳給你 0 鈴錢。
/**
* Class SpoiledSpecification.
*/
class SpoiledSpecification implements Specification
{
/**
* @var Specification[]
*/
protected array $turnips;
/**
* SpoiledSpecification constructor.
*
* @param Specification[] $turnips
*/
public function __construct(Specification ...$turnips)
{
$this->turnips = $turnips;
}
/**
* @return int
*/
public function calculatePrice(): int
{
return 0;
}
}
最後我們要寫個測試,來測試規格模式是不是正確的,主要分別為單顆大頭菜與多顆大頭菜的狀況下,以及正常、壞掉的兩種規格模式的測試。
- 單顆大頭菜使用正常規格模組,是否能正常計算出鈴錢價格。
- 多顆大頭菜使用正常規格模組,是否能正常計算出鈴錢價格。
- 單顆大頭菜使用正常規格模組,再套用壞掉的規格,是否能正常計算出壞掉的鈴錢價格。
- 多顆大頭菜使用正常規格模組,再套用壞掉的規格,是否能正常計算出壞掉的鈴錢價格。
SpecificationPatternTest.php
/**
* Class SpecificationPatternTest.
*/
class SpecificationPatternTest extends TestCase
{
/**
* @test
*/
public function test_single_turnips()
{
$turnips = new Turnips(100, 40);
$specification = new TurnipsSpecification($turnips);
$this->assertEquals(4000, $specification->calculatePrice());
}
/**
* @test
*/
public function test_multi_turnips()
{
$turnips_A = new Turnips(100, 40);
$turnips_B = new Turnips(90, 20);
$turnips_C = new Turnips(110, 20);
$specification = new TurnipsSpecification($turnips_A, $turnips_B, $turnips_C);
$this->assertEquals(8000, $specification->calculatePrice());
}
/**
* @test
*/
public function test_single_spoiled()
{
$turnips = new Turnips(100, 40);
$specification = new TurnipsSpecification($turnips);
$spoiled = new SpoiledSpecification($specification);
$this->assertEquals(0, $spoiled->calculatePrice());
}
/**
* @test
*/
public function test_multi_spoiled()
{
$turnips_A = new Turnips(100, 40);
$turnips_B = new Turnips(90, 20);
$turnips_C = new Turnips(110, 20);
$specification = new TurnipsSpecification($turnips_A, $turnips_B, $turnips_C);
$spoiled = new SpoiledSpecification($specification);
$this->assertEquals(0, $spoiled->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.
==> ...fResponsibilitiesTest ✔ ✔ ✔
==> CommandPatternTest ✔
==> IteratorPatternTest ✔ ✔ ✔ ✔
==> MediatorPatternTest ✔ ✔ ✔
==> MementoPatternTest ✔
==> NullObjectPatternTest ✔ ✔ ✔ ✔
==> ObserverPatternTest ✔
==> SpecificationPatternTest ✔ ✔ ✔ ✔
==> AbstractFactoryTest ✔ ✔ ✔ ✔
==> BuilderPatternTest ✔ ✔ ✔ ✔
==> FactoryMethodTest ✔ ✔ ✔ ✔
==> PoolPatternTest ✔ ✔
==> PrototypePatternTest ✔ ✔
==> SimpleFactoryTest ✔ ✔ ✔ ✔
==> SingletonPatternTest ✔
==> StaticFactoryTest ✔ ✔ ✔ ✔ ✔
==> AdapterPatternTest ✔ ✔
==> BridgePatternTest ✔ ✔ ✔
==> CompositePatternTest ✔ ✔ ✔
==> DataMapperTest ✔ ✔
==> DecoratorPatternTest ✔ ✔
==> DependencyInjectionTest ✔ ✔ ✔
==> FacadePatternTest ✔
==> FluentInterfaceTest ✔
==> FlyweightPatternTest ✔
==> ProxyPatternTest ✔ ✔
==> RegistryPatternTest ✔ ✔ ✔ ✔ ✔
Time: 00:00.036, Memory: 8.00 MB
OK (72 tests, 141 assertions)