責任鏈模式 Chain of Responsibilities
責任鏈模式，有一系列的命令物件及處理物件，常見於需要被連續處理的地方上，舉例來說，假設今天收購箱、商店收購大頭菜時，多了一些條件，你必須先把大頭菜拿去收購箱收購，並且收購箱子會有鈴錢價格打 8 折的情形，剩下有多餘的大頭菜才能拿去給商店收購。
UML
實作
首先我們要先把背包(Bag)、大頭菜(Turnips)這兩個東西給實作出來，先從大頭菜開始，一樣建立簡單的鈴錢、數量以及獲取賦予方法。
Turnips.php
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class Turnips
{
protected int $price;
protected int $count;
public function __construct(int $price, int $count)
{
$this->setPrice($price);
$this->setCount($count);
}
public function setPrice(int $price)
{
$this->price = $price;
}
public function setCount(int $count)
{
$this->count = $count;
}
public function getPrice(): int
{
return $this->price;
}
public function getCount(): int
{
return $this->count;
}
}
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再來要建立背包(Bag)這個物件，裡面主要會放置兩個主要的物件，分別是大頭菜($turnips: Turnips)以及鈴錢($bells: int)，並且擁有簡單的取得(get)及賦予(set)方法。
Bag.php
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class Bag
{
protected Turnips $turnips;
protected int $bells = 0;
public function setTurnips(Turnips $turnips)
{
$this->turnips = $turnips;
}
public function setBells(int $bells)
{
$this->bells = $bells;
}
public function getTurnips(): Turnips
{
return $this->turnips;
}
public function getBells(): int
{
return $this->bells;
}
}
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再來我們要建立主要的處理物件(Handler)，這個處理物件是抽象介面，主要先實作出上層的處理物件是什麼，其次需要繼承的子類別需要實作賣大頭菜的方法。
Handler.php
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abstract class Handler
{
protected $upper;
public function setUpperHandler(Handler $upper)
{
$this->upper = $upper;
}
abstract public function sellTurnips(Bag $bag): Bag;
}
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最後我們要建立收購箱(Box)的處理物件，以及商店(Store)的處理物件，收購箱最多只能賣 20 顆大頭菜，並且收購價格都會打 8 折，如果背包裡有剩餘的大頭菜，那麼收購箱就會去呼叫上層處理物件去處理剩下的大頭菜，而在這邊收購箱(Box)的上層物件就會是商店(Store)。
BoxHandler.php
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class BoxHandler extends Handler
{
public function sellTurnips(Bag $bag): Bag
{
$bells = function(int $oldBells, int $price, int $count) {
$_bells = ($price * $count) * 0.8;
$_bells += $oldBells;
return $_bells;
};
if ($bag->getTurnips()->getCount() >= 20) {
$newBells = $bells($bag->getBells(), $bag->getTurnips()->getPrice(), 20);
$bag->setBells($newBells);
$bag->getTurnips()->setCount($bag->getTurnips()->getCount() - 20);
return $this->upper->sellTurnips($bag);
}
$newBells = $bells($bag->getBells(), $bag->getTurnips()->getPrice(), $bag->getTurnips()->getCount());
$bag->setBells($newBells);
$bag->getTurnips()->setCount(0);
return $bag;
}
}
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StoreHandler.php
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class StoreHandler extends Handler
{
public function sellTurnips(Bag $bag): Bag
{
$bells = $bag->getTurnips()->getPrice() * $bag->getTurnips()->getCount();
$bells += $bag->getBells();
$bag->getTurnips()->setCount(0);
$bag->setBells($bells);
return $bag;
}
}
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測試
最後我們要來進行一連串的測試，來測試大頭菜責任鏈模式是否可以正常運作，所以會有幾些測試項目需要執行：
- 測試一次賣 40 顆大頭菜，是否會有 20 顆大頭菜在商店被賣出。
- 測試一次賣 20 顆大頭菜，是否全部的大頭菜都只會在收購箱被賣出。
- 測試賣兩次大頭菜，所賣出的鈴錢是否正確。
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class ChainOfResponsibilitiesTest extends TestCase
{
protected $bag;
protected $handler;
protected function setUp(): void
{
parent::setUp();
$this->bag = new Bag();
$this->handler = new BoxHandler();
$storeHandler = new StoreHandler();
$this->handler->setUpperHandler($storeHandler);
}
public function test_sell_turnips_to_store()
{
$this->bag->setTurnips(new Turnips(100, 40));
$this->bag = $this->handler->sellTurnips($this->bag);
$this->assertEquals(3600, $this->bag->getBells());
}
public function test_sell_turnips_to_box()
{
$this->bag->setTurnips(new Turnips(80, 20));
$this->bag = $this->handler->sellTurnips($this->bag);
$this->assertEquals(1280, $this->bag->getBells());
}
public function test_sell_turnips_to_box_and_store()
{
$this->bag->setTurnips(new Turnips(80, 20));
$this->bag = $this->handler->sellTurnips($this->bag);
$this->assertEquals(1280, $this->bag->getBells());
$this->bag->setTurnips(new Turnips(100, 60));
$this->bag = $this->handler->sellTurnips($this->bag);
$this->assertEquals(6880, $this->bag->getBells());
}
}
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最後測試的執行結果會獲得如下：
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| ==> ...fResponsibilitiesTest ✔ ✔ ✔
==> AbstractFactoryTest ✔ ✔ ✔ ✔
==> BuilderPatternTest ✔ ✔ ✔ ✔
==> FactoryMethodTest ✔ ✔ ✔ ✔
==> PoolPatternTest ✔ ✔
==> PrototypePatternTest ✔ ✔
==> SimpleFactoryTest ✔ ✔ ✔ ✔
==> SingletonPatternTest ✔
==> StaticFactoryTest ✔ ✔ ✔ ✔ ✔
==> AdapterPatternTest ✔ ✔
==> BridgePatternTest ✔ ✔ ✔
==> CompositePatternTest ✔ ✔ ✔
==> DataMapperTest ✔ ✔
==> DecoratorPatternTest ✔ ✔
==> DependencyInjectionTest ✔ ✔ ✔
==> FacadePatternTest ✔
==> FluentInterfaceTest ✔
==> FlyweightPatternTest ✔
==> ProxyPatternTest ✔ ✔
==> RegistryPatternTest ✔ ✔ ✔ ✔ ✔
Time: 00:00.066, Memory: 6.00 MB
OK (54 tests, 120 assertions)
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完整程式碼
設計模式不難，找回快樂而已，以大頭菜為例。
參考文獻