关于后端:结构型设计模式外观-Facade

简介

外观模式特点是屏蔽后端简单的实现逻辑，将其整合成简略的一个或几个接口提供进来，client 只需与 Facade 层提供的简略接口交互即可。

例如银行办业务，前面波及到很多财务细节，但用户面对的就是一个窗口业务员。

角色

• Facade 外观层
• Subsystem 负责具体事务的子系统们

类图

代码

class Facade{    protected $subsystem1;    protected $subsystem2;    public function __construct(        Subsystem1 $subsystem1 = null,        Subsystem2 $subsystem2 = null    ) {        $this->subsystem1 = $subsystem1 ?: new Subsystem1();        $this->subsystem2 = $subsystem2 ?: new Subsystem2();    }    public function operation(): string    {        $result = "Facade initializes subsystems:\n";        $result .= $this->subsystem1->operation1();        $result .= $this->subsystem2->operation1();        $result .= "Facade orders subsystems to perform the action:\n";        $result .= $this->subsystem1->operationN();        $result .= $this->subsystem2->operationZ();        return $result;    }}class Subsystem1{    public function operation1(): string    {        return "Subsystem1: Ready!\n";    }    public function operationN(): string    {        return "Subsystem1: Go!\n";    }}class Subsystem2{    public function operation1(): string    {        return "Subsystem2: Get ready!\n";    }    public function operationZ(): string    {        return "Subsystem2: Fire!\n";    }}function clientCode(Facade $facade){    echo $facade->operation();}$subsystem1 = new Subsystem1();$subsystem2 = new Subsystem2();$facade = new Facade($subsystem1, $subsystem2);clientCode($facade);

output:

Facade initializes subsystems:Subsystem1: Ready!Subsystem2: Get ready!Facade orders subsystems to perform the action:Subsystem1: Go!Subsystem2: Fire!

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