中介者模式，在兩個不同的封裝物件之間，作為中間進行交互的模式，可以減少物件之間的依賴關係，並且降低耦合性問題，舉例來說有背包(Bag)與商店(Store)這兩個物件，你會從背包(Bag)當中拿出鈴錢(Bells)去商店(Store)購買大頭菜(Turnips)，但它們應該要各自其職，不要太過於互相依賴，因此你會需要有個中間控制這些物件的中介者(Mediator)。
首先我們不外乎先製作出大頭菜(Turnips)物件，只需要賦予簡單計算數量的功能即可。
Turnips.php
/**
* Turnips
*/
class Turnips
{
/**
* @var int
*/
protected int $count;
/**
* Turnips constructor.
*
* @param int $count
*/
public function __construct(int $count)
{
$this->setCount($count);
}
/**
* @param int $count
*/
public function setCount(int $count)
{
$this->count = $count;
}
/**
* @return int
*/
public function getCount(): int
{
return $this->count;
}
}接下來我們要做出背包(Bag)以及商店(Store)這兩個物件，因為這兩個物件會進行交互，所以需要有一個抽象類別去把中介者(Mediator)帶入，這裡稱之為協調同事(Colleague)物件，所以我們要先實作出協調同事(Colleague)這項物件，再去實作背包(Bag)以及商店(Store)這兩個物件，並且繼承協調同事(Colleague)這個抽象。
Colleague.php
/**
* Abstract Colleague.
*/
abstract class Colleague
{
/**
* @var Mediator
*/
protected Mediator $mediator;
/**
* @param Mediator $mediator
*/
public function setMediator(Mediator $mediator)
{
$this->mediator = $mediator;
}
}Bag.php
/**
* Class Bag.
*/
class Bag extends Colleague
{
/**
* @var Bells
*/
protected $bells;
/**
* @var Turnips
*/
protected $turnips;
/**
* Bag constructor.
*/
public function __construct()
{
$this->bells = new Bells(0);
$this->turnips = new Turnips(0);
}
/**
* @return int
*/
public function getBells(): int
{
return $this->bells->getBells();
}
/**
* @return int
*/
public function getTurnips(): int
{
return $this->turnips->getCount();
}
/**
* @param int $bells
*/
public function setBells(int $bells)
{
echo "[背包] 剩下 $bells 鈴錢。";
$this->bells->setBells($bells);
}
/**
* @param int $count
*/
public function setTurnips(int $count)
{
echo "[背包] 剩下 $count 顆大頭菜。";
$this->turnips->setCount($count);
}
}Store.php
use InvalidArgumentException;
/**
* Class Store.
*/
class Store extends Colleague
{
/**
* @param int $price
* @param int $count
*
* @throws InvalidArgumentException
* @return Turnips
*/
public function buyTurnips(int $price, int $count)
{
$total = $price * $count;
if ($this->mediator->getBells() >= $total) {
/**
* 跟商店(Store)買大頭菜(Turnips)，並且將大頭菜放入背包(Bag)當中。
*/
$this->mediator->setBells($this->mediator->getBells() - $total);
echo "[商店] 收到了 $total 鈴錢。";
echo "[商店] 賣出了 $count 顆大頭菜。";
$this->mediator->setTurnips($this->mediator->getTurnips() + $count);
return;
}
throw new InvalidArgumentException('[錯誤] 您背包裡的鈴錢不足，無法購買大頭菜。');
}
/**
* @param int $price
* @param int $count
*
* @throws InvalidArgumentException
* @return int
*/
public function sellTurnips(int $price, int $count)
{
if ($this->mediator->getTurnips() >= $count) {
/**
* 跟商店(Store)賣大頭菜(Turnips)，並且將鈴錢放入背包(Bag)當中。
*/
$this->mediator->setTurnips($this->mediator->getTurnips() - $count);
echo "[商店] 收購了 $count 顆大頭菜。";
$total = $price * $count;
echo "[商店] 支出了 $total 鈴錢。";
$this->mediator->setBells($this->mediator->getBells() + $total);
return;
}
throw new InvalidArgumentException('[錯誤] 您背包裡的大頭菜不足，無法販賣大頭菜。');
}
}最後我們要來把中介者(Mediator)實作出來，這個中介者(Mediator)會作為背包(Bag)以及商店(Store)之間交互的載體，所以在實作之前先定義它的介面(Interface)出來。
MediatorInterface.php
/**
* Interface MediatorInterface.
*/
interface MediatorInterface
{
/**
* @return int
*/
public function getBells(): int;
/**
* @return int
*/
public function getTurnips(): int;
/**
* @param int $bells
*/
public function setBells(int $bells);
/**
* @param int $count
*/
public function setTurnips(int $count);
/**
* @param int $price
* @param int $count
*/
public function buyTurnips(int $price, int $count);
/**
* @param int $price
* @param int $count
*/
public function sellTurnips(int $price, int $count);
}最後去實作出背包(Bag)與商店(Store)的中介者(Mediator)，背包(Bag)主要控制鈴錢(Bells)以及大頭菜(Turnips)，商店(Store)則是會透過中介者(Mediator)去向背包(Bag)去索取鈴錢(Bells)以及大頭菜(Turnips)，而不是真的去觸及背包(Bag)，減少物件之間的依賴關係。
BagStoreMediator.php
use InvalidArgumentException;
/**
* Class BagStoreMediator.
*/
class BagStoreMediator implements MediatorInterface
{
/**
* @var Bag
*/
protected Bag $bag;
/**
* @var Store
*/
protected Store $store;
/**
* BagStoreMediator constructor.
*
* @param Bag $bag
* @param Store $store
*/
public function __construct(Bag $bag, Store $store)
{
$this->bag = $bag;
$this->store = $store;
$this->bag->setMediator($this);
$this->store->setMediator($this);
}
/**
* @return int
*/
public function getBells(): int
{
return $this->bag->getBells();
}
/**
* @return int
*/
public function getTurnips(): int
{
return $this->bag->getTurnips();
}
/**
* @param int $bells
*/
public function setBells(int $bells)
{
$this->bag->setBells($bells);
}
/**
* @param int $count
*/
public function setTurnips(int $count)
{
$this->bag->setTurnips($count);
}
/**
* @param int $price
* @param int $count
*
* @throws InvalidArgumentException
*/
public function buyTurnips(int $price, int $count)
{
$total = $price * $count;
if ($this->bag->getBells() >= $total) {
echo "[玩家] 您購買了 $count 顆大頭菜，每顆單價 $price 鈴錢，總共 $total 鈴錢。";
$this->store->buyTurnips($price, $count);
return;
}
throw new InvalidArgumentException('[錯誤] 您的大頭菜不足，無法購買大頭菜。');
}
/**
* @param int $price
* @param int $count
*
* @throws InvalidArgumentException
*/
public function sellTurnips(int $price, int $count)
{
$total = $price * $count;
if ($this->bag->getTurnips() >= $count) {
echo "[玩家] 您販賣了 $count 顆大頭菜，每顆單價 $price 鈴錢，總共 $total 鈴錢。";
$this->store->sellTurnips($price, $count);
return;
}
throw new InvalidArgumentException('[錯誤] 您的大頭菜不足，無法販賣大頭菜。');
}
}最後根據上面的中介者，我們要做幾個簡單的測試，第一件事是測試進行買賣大頭菜時，所產生的 Log 順序、資料是否正確，其次是例外錯誤 InvalidArgumentException 是否有確實。
MediatorPatternTest.php
/**
* Class MediatorPatternTest.
*/
class MediatorPatternTest extends TestCase
{
/**
* @test
*/
public function test_buy_and_sell_turnips()
{
$mediator = new BagStoreMediator(new Bag(), new Store());
$mediator->setBells(10000);
$this->expectOutputString(implode(array(
"[背包] 剩下 10000 鈴錢。",
"[玩家] 您購買了 40 顆大頭菜，每顆單價 100 鈴錢，總共 4000 鈴錢。",
"[背包] 剩下 6000 鈴錢。",
"[商店] 收到了 4000 鈴錢。",
"[商店] 賣出了 40 顆大頭菜。",
"[背包] 剩下 40 顆大頭菜。",
"[玩家] 您販賣了 20 顆大頭菜，每顆單價 200 鈴錢，總共 4000 鈴錢。",
"[背包] 剩下 20 顆大頭菜。",
"[商店] 收購了 20 顆大頭菜。",
"[商店] 支出了 4000 鈴錢。",
"[背包] 剩下 10000 鈴錢。",
)));
$mediator->buyTurnips(100, 40);
$mediator->sellTurnips(200, 20);
}
/**
* @test
*/
public function test_buy_turnips_overflow()
{
$this->expectException(InvalidArgumentException::class);
$mediator = new BagStoreMediator(new Bag(), new Store());
$mediator->buyTurnips(100, 200);
}
/**
* @test
*/
public function test_sell_turnips_overflow()
{
$this->expectException(InvalidArgumentException::class);
$mediator = new BagStoreMediator(new Bag(), new Store());
$mediator->sellTurnips(100, 40);
}
}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 ✔ ✔ ✔
==> AbstractFactoryTest ✔ ✔ ✔ ✔
==> BuilderPatternTest ✔ ✔ ✔ ✔
==> FactoryMethodTest ✔ ✔ ✔ ✔
==> PoolPatternTest ✔ ✔
==> PrototypePatternTest ✔ ✔
==> SimpleFactoryTest ✔ ✔ ✔ ✔
==> SingletonPatternTest ✔
==> StaticFactoryTest ✔ ✔ ✔ ✔ ✔
==> AdapterPatternTest ✔ ✔
==> BridgePatternTest ✔ ✔ ✔
==> CompositePatternTest ✔ ✔ ✔
==> DataMapperTest ✔ ✔
==> DecoratorPatternTest ✔ ✔
==> DependencyInjectionTest ✔ ✔ ✔
==> FacadePatternTest ✔
==> FluentInterfaceTest ✔
==> FlyweightPatternTest ✔
==> ProxyPatternTest ✔ ✔
==> RegistryPatternTest ✔ ✔ ✔ ✔ ✔
Time: 00:00.173, Memory: 6.00 MB
OK (62 tests, 129 assertions)