代理模式，它可以作為需要被保護的物件的介面，若以檔案權限來比喻的話，就是對主要物件套上一層代理，你可以在代理上實作控制權限，像是其代理僅有讀取、執行的權限，並沒有刪除、修改的權限，並防止直接接觸實際物件，換作大頭菜來講的話，大頭菜的本質就是大頭菜，大頭菜就頂多提供數量堆積的功能，鈴錢的計算要在代理介面上實作。
所以我們要先來實作大頭菜介面，並且僅提供大頭菜總數計算的功能。
TurnipsInterface.php
/**
* Interface TurnipsInterface.
*/
interface TurnipsInterface
{
/**
* @param int $count
*/
public function setCount(int $count);
/**
* @return int
*/
public function getCount(): int;
}Turnips.php
/**
* Class Turnips.
*/
class Turnips implements TurnipsInterface
{
/**
* @var int
*/
protected int $count = 0;
/**
* @param int $count
*/
public function setCount(int $count)
{
$this->count = $count;
}
/**
* @return int
*/
public function getCount(): int
{
return $this->count;
}
}最後我們要製作大頭菜的代理，大頭菜代理繼承了大頭菜，並且再額外提供了鈴錢價格計算的功能。
TurnipsProxy.php
/**
* Class TurnipsProxy.
*/
class TurnipsProxy extends Turnips implements TurnipsInterface
{
/**
* @var int
*/
protected int $price = 0;
/**
* @var int
*/
protected ?int $total = null;
/**
* TurnipsProxy constructor.
*
* @param int $price
* @param int $count
*/
public function __construct(int $price, int $count)
{
$this->setPrice($price);
$this->setCount($count);
}
/**
* @param int $price
*/
public function setPrice(int $price)
{
$this->price = $price;
}
/**
* @return int
*/
public function getPrice(): int
{
return $this->price;
}
/**
* @return int
*/
public function calculateTotal(): int
{
if ($this->total === null)
{
$this->total = $this->getPrice() * $this->getCount();
}
return $this->total;
}
}最後我們要來測試代理大頭菜的功能，會有幾個大項目需要測試：
- 透過代理來計算鈴錢總價。
- 鈴錢總價只會計算一次，並不會因為後續更改而變更。
ProxyPatternTest.php
/**
* Class ProxyPatternTest.
*/
class ProxyPatternTest extends TestCase
{
/**
* 透過代理來計算鈴錢總價。
*
* @test
*/
public function test_proxy_calculate_price()
{
$turnips = new TurnipsProxy(100, 40);
$this->assertEquals(4000, $turnips->calculateTotal());
}
/**
* 透過代理來計算鈴錢總價，並且鈴錢總價只會計算一次，並不會因為後續更改而變更。
*
* @test
*/
public function test_proxy_will_only_execute_calculate_price_once()
{
$turnips = new TurnipsProxy(100, 40);
$this->assertEquals(4000, $turnips->calculateTotal());
$turnips->setPrice(200);
$turnips->setCount(30);
$this->assertEquals(4000, $turnips->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 ✔
==> ProxyPatternTest ✔ ✔
Time: 00:00.029, Memory: 6.00 MB
OK (46 tests, 110 assertions)