行为型设计模式 - 中介者 Mediator
作者：菜皮日记
- 2023-09-08 北京
本文字数：1532 字
阅读完需：约 5 分钟
简介
通过引入一个中介者，将对象之间两两交互的情景，改为每个对象都是与中介者交互，即将网状关系改成了星状关系。缺点是中介者逻辑会很臃肿。
当系统中出现多对多的情况时，应该先考虑设计是否合理，而尽量不要直接使用中介者。
角色
抽象 Mediator 中介者
具体 Mediator 中介者
抽象 Component
具体 Component
类图
中介者需要了解所有 Component，而且 notify 中要编写处理所有可能发生的情况，Mediator 是一个非常臃肿的类。
类图
代码
interface Mediator{ public function notify(object $sender, string $event): void;}
class ConcreteMediator implements Mediator{ private $component1;
private $component2;
public function __construct(Component1 $c1, Component2 $c2) { $this->component1 = $c1; $this->component1->setMediator($this); $this->component2 = $c2; $this->component2->setMediator($this); }
public function notify(object $sender, string $event): void { if ($event == "A") { echo "Mediator reacts on A and triggers following operations:\n"; $this->component2->doC(); }
if ($event == "D") { echo "Mediator reacts on D and triggers following operations:\n"; $this->component1->doB(); $this->component2->doC(); } }}
class BaseComponent{ protected $mediator;
public function __construct(Mediator $mediator = null) { $this->mediator = $mediator; }
public function setMediator(Mediator $mediator): void { $this->mediator = $mediator; }}
class Component1 extends BaseComponent{ public function doA(): void { echo "Component 1 does A.\n"; $this->mediator->notify($this, "A"); }
public function doB(): void { echo "Component 1 does B.\n"; $this->mediator->notify($this, "B"); }}
class Component2 extends BaseComponent{ public function doC(): void { echo "Component 2 does C.\n"; $this->mediator->notify($this, "C"); }
public function doD(): void { echo "Component 2 does D.\n"; $this->mediator->notify($this, "D"); }}
$c1 = new Component1();$c2 = new Component2();$mediator = new ConcreteMediator($c1, $c2);
echo "Client triggers operation A.\n";$c1->doA();
echo "\n";echo "Client triggers operation D.\n";$c2->doD();
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output:
Client triggers operation A.Component 1 does A.Mediator reacts on A and triggers following operations:Component 2 does C.
Client triggers operation D.Component 2 does D.Mediator reacts on D and triggers following operations:Component 1 does B.Component 2 does C.
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