外觀模式，或者稱作門面模式，一種把複雜邏輯給包裝起來的一種模式，舉個例子來說，今天已經不單只是計算大頭菜了，而是你有個背包(Bag)要先放入鈴錢(Bells)，然後拿出鈴錢從曹賣(DaisyMae)手中購買大頭菜，並且把大頭菜賣給 Nook 商店(Store)，牽涉到許多的細節，透過外觀模式來將複雜的操作集中成幾個簡單的動作。
首先我們先慣例定義一下主角大頭菜(Turnips)，在這邊只需要給予價格、數量即可。
Turnips.php
/**
* Class Turnips
*/
class Turnips
{
/**
* @var int
*/
protected $price;
/**
* @var int
*/
protected $count;
/**
* 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 setPrice(int $price)
{
$this->price = $price;
}
/**
* @return int
*/
public function setCount(int $count)
{
$this->count = $count;
}
/**
* @return int
*/
public function getPrice(): int
{
return $this->price;
}
/**
* @return int
*/
public function getCount(): int
{
return $this->count;
}
}
接下來我們要定義背包(Bag)，會需要可以放入鈴錢、大頭菜，並且可以取用，在取出的同時必須做到扣除背包裡鈴錢或大頭菜的數量。
BagInterface.php
/**
* Interface BagInterface.
*/
interface BagInterface
{
/**
* @param int $bells
*/
public function setBells(int $bells): int;
/**
* @return int
*/
public function getBells(int $bells): int;
/**
* @param Turnips $turnips
*/
public function setTurnips(Turnips $turnips): Turnips;
/**
* @return Turnips
*/
public function getTurnips(int $count): Turnips;
}
Bag.php
use InvalidArgumentException;
/**
* Class Bag.
*/
class Bag implements BagInterface
{
/**
* @var int
*/
protected $bells = 0;
/**
* @var Turnips
*/
protected $turnips;
/**
* @param int $bells
*/
public function setBells(int $bells): int
{
$this->bells += $bells;
return $this->bells;
}
/**
* @throws InvalidArgumentException
* @return int
*/
public function getBells(int $bells): int
{
if ($this->bells >= $bells) {
$this->bells -= $bells;
return $this->bells;
}
throw new InvalidArgumentException('背包裡頭沒有那麼多的鈴錢。');
}
/**
* @param Turnips
*/
public function setTurnips(Turnips $turnips): Turnips
{
$this->turnips = $turnips;
return $this->turnips;
}
/**
* @throws InvalidArgumentException
* @return Turnips
*/
public function getTurnips(int $count): Turnips
{
if ($this->turnips->getCount() >= $count) {
$newCount = $this->turnips->getCount() - $count;
$this->turnips->setCount($newCount);
return new Turnips($this->turnips->getPrice(), $count);
}
throw new InvalidArgumentException('背包裡頭沒有那麼多的大頭菜。');
}
}
再來我們要定義曹賣(DaisyMae)，曹賣的功能很簡單，就只需要購買大頭菜即可，當玩家購買大頭菜時，曹賣必須給玩家大頭菜。
DaisyMaeInterface.php
/**
* Interface DaisyMaeInterface.
*/
interface DaisyMaeInterface
{
/**
* @param int $price
* @param int $count
*
* @return Turnips
*/
public function buy(int $price, int $count): Turnips;
}
DaisyMae.php
/**
* Class DaisyMae.
*/
class DaisyMae implements DaisyMaeInterface
{
/**
* @param int $price
* @param int $count
*
* @return Turnips
*/
public function buy(int $price, int $count): Turnips
{
return new Turnips($price, $count);
}
}
再來我們需要建立 Nook 商店(Store)，商店的功能也很簡單，就是把大頭菜賣給商店就可以了。
StoreInterface.php
/**
* Interface StoreInterface.
*/
interface StoreInterface
{
/**
* @param Turnips $turnips
* @param int $price
*
* @return int
*/
public function sell(Turnips $turnips, int $price): int;
}
Store.php
/**
* Class Store.
*/
class Store implements StoreInterface
{
/**
* @param Turnips $turnips
* @param int $price
*
* @return int
*/
public function sell(Turnips $turnips, int $price): int
{
return $turnips->getCount() * $price;
}
}
最後我們需要來建立外觀(Facade)，其功能是負責處理複雜邏輯，將其化為簡單的動作，這裡我們需要幾個簡單的動作，分別是：
Facade.php
/**
* Class Facade.
*/
class Facade
{
/**
* @var BagInterface
*/
protected $bag;
/**
* @var StoreInterface
*/
protected $store;
/**
* @var DaisyMaeInterface
*/
protected $daisyMae;
/**
* Facade constructor.
*
* @param BagInterface $bag
* @param StoreInterface $store
* @param DaisyMaeInterface $daisyMae
*/
public function __construct(BagInterface $bag, StoreInterface $store, DaisyMaeInterface $daisyMae)
{
$this->bag = $bag;
$this->store = $store;
$this->daisyMae = $daisyMae;
}
/**
* @param int $bells
*/
public function takeupBells(int $bells): int
{
return $this->bag->setBells($bells);
}
/**
* @param int $bells
*
* @return int
*/
public function takeoutBells(int $bells): int
{
return $this->bag->getBells($bells);
}
/**
* @param int $price
* @param int $count
*
* @return int
*/
public function buyTurnips(int $price, int $count): int
{
$this->bag->getBells($price * $count);
$turnips = $this->daisyMae->buy($price, $count);
$this->bag->setTurnips($turnips);
return $this->bag->setBells(0);
}
/**
* @param int $price
*
* @return int
*/
public function sellTurnips(int $price, int $count): int
{
$turnips = $this->bag->getTurnips($count);
$bells = $this->store->sell($turnips, $price);
return $this->bag->setBells($bells);
}
}
撰寫完外觀模式後，我們需要測試程式邏輯是否正確，因此接下來也會有幾個大項目需要測試：
FacadePatternTest.php
/**
* Class FacadePatternTest.
*/
class FacadePatternTest extends TestCase
{
/**
* @test
*/
public function test_buy_and_sell_turnips()
{
$bag = new Bag();
$store = new Store();
$daisyMae = new DaisyMae();
$facade = new Facade($bag, $store, $daisyMae);
// 在背包裡塞入 10,000 鈴錢
$this->assertEquals(10000, $facade->takeupBells(10000));
// 購買 40 顆單價 100 鈴錢的大頭菜
$this->assertEquals(6000 ,$facade->buyTurnips(100, 40));
// 以 400 鈴錢賣出 20 顆大頭菜
$this->assertEquals(14000 ,$facade->sellTurnips(400, 20));
// 從背包拿出 10,000 鈴錢
$this->assertEquals(4000 ,$facade->takeoutBells(10000));
// 再以 600 鈴錢賣出 20 顆大頭菜
$this->assertEquals(16000 ,$facade->sellTurnips(600, 20));
}
}
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 ✔
Time: 00:00.028, Memory: 6.00 MB
OK (42 tests, 93 assertions)
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