橋接模式，將實作體系與抽象體系分離開來，讓兩者能各自更動各自演進，就有點像是大頭菜有分健康的大頭菜及壞掉的大頭菜，你的島上有這兩種大頭菜，但是健康的大頭菜過了一個禮拜都沒賣掉的話，他就會變成壞掉的大頭菜了。
首先我們要來把大頭菜做出來，因此會有定義大頭菜介面 Interface、建立健康的大頭菜及壞掉的大頭菜。
TurnipsInterface.php
/**
* Interface TurnipsInterface.
*/
interface TurnipsInterface
{
public function calculatePrice(): int;
}Turnips.php
/**
* Class Turnips.
*/
class Turnips implements TurnipsInterface
{
/**
* @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 = $count;
}
/**
* @return int
*/
public function calculatePrice(): int
{
if (isset($this->price) && isset($this->count)) {
return $this->price * $this->count;
} else {
return 0;
}
}
}Spoiled.php
/**
* Class Spoiled.
*/
class Spoiled implements TurnipsInterface
{
/**
* @var int
*/
protected $price;
/**
* @var int
*/
protected $count;
/**
* Spoiled constructor.
*
* @param int $price
* @param int $count
*/
public function __construct(int $price, int $count)
{
$this->price = $price;
$this->count = $count;
}
/**
* @return int
*/
public function calculatePrice(): int
{
if (isset($this->price) && isset($this->count)) {
return 0 * $this->count;
} else {
return 0;
}
}
}接下來我們要建立所謂的橋樑，這裡有個重要的地方是實作(Implementation)，功能是來去替換大頭菜的類別。
BaseService.php
/**
* Class BaseService.
*/
abstract class BaseService
{
/**
* @var TurnipsInterface
*/
protected $implementation;
/**
* @param TurnipsInterface $turnips
*/
public function __construct(TurnipsInterface $turnips)
{
$this->implementation = $turnips;
}
/**
* @param TurnipsInterface $turnips
*/
public function setImplementation(TurnipsInterface $turnips)
{
$this->implementation = $turnips;
}
abstract public function calculatePrice();
}TurnipsService.php
/**
* Class TurnipsService.
*/
class TurnipsService extends BaseService
{
/**
* @return int
*/
public function calculatePrice()
{
return $this->implementation->calculatePrice();
}
}最後我們要來寫幾些測試項目，主要測試建立 Service 並且執行計算，以及是否能夠替換大頭菜類別，並且計算。
- 測試是否能建立 Service 並把健康的大頭菜塞進去，然後計算鈴錢。
- 測試是否能建立 Service 並把壞掉的大頭菜塞進去，然後計算鈴錢。
- 測試是否能建立 Service 並把健康的大頭菜塞進去，然後計算鈴錢，再把大頭菜替換成壞掉的大頭菜，再計算一次鈴錢。
BridgePatternTest.php
/**
* Class BridgePatternTest.
*/
class BridgePatternTest extends TestCase
{
/**
* 測試是否能建立 Service 並把健康的大頭菜塞進去，然後計算鈴錢。
*
* @test
*/
public function test_can_calculate_price_for_turnips()
{
$service = new TurnipsService(new Turnips(100, 40));
$this->assertEquals(4000, $service->calculatePrice());
}
/**
* 測試是否能建立 Service 並把壞掉的大頭菜塞進去，然後計算鈴錢。
*
* @test
*/
public function test_can_calculate_price_for_spoiled()
{
$service = new TurnipsService(new Spoiled(100, 40));
$this->assertEquals(0, $service->calculatePrice());
}
/**
* 測試是否能建立 Service 並把健康的大頭菜塞進去，然後計算鈴錢，
* 再把大頭菜替換成壞掉的大頭菜，再計算一次鈴錢。
*
* @test
*/
public function test_can_calculate_price_for_turnips_and_spoiled()
{
$service = new TurnipsService(new Turnips(100, 40));
$this->assertEquals(4000, $service->calculatePrice());
$service->setImplementation(new Spoiled(100, 40));
$this->assertEquals(0, $service->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 ✔ ✔ ✔
Time: 00:00.027, Memory: 6.00 MB
OK (31 tests, 76 assertions)