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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,行将网状关系改成了星状关系。毛病是中介者逻辑会很臃肿。
当零碎中呈现多对多的状况时,应该先思考设计是否正当,而尽量不要间接应用中介者。
角色
- 形象 Mediator 中介者
- 具体 Mediator 中介者
- 形象 Component
- 具体 Component
类图
中介者须要理解所有 Component,而且 notify 中要编写解决所有可能产生的状况,Mediator 是一个十分臃肿的类。
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();
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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