结构型设计模式-适配器 Adapter

date: April 13, 2021
slug: design-pattern-adapter
status: Published
tags: 设计模式
type: Page

简介

适配器模式是一种结构型设计模式， 它能使接口不兼容的对象能够相互合作

角色

• Client 接口 / Target 目标接口

  用户使用的接口

• Adaptee

  被适配的对象，原有方法不能直接给 client 使用

• Adapter

  适配器，实现 Target 接口，将 Adaptee 的方法改造成兼容 client 的形式，供 client使用

类图

图示，Adapter 持有 Service 对象实例，method 方法实现自 Client Interface，使 client 可以调用，method 内部逻辑则将 client 的入参转换后交给 service 处理

代码

class Target
{
    public function request(): string
    {
        return "Target: The default target's behavior.";
    }
}

class Adaptee
{
    public function specificRequest(): string
    {
        return ".eetpadA eht fo roivaheb laicepS";
    }
}

class Adapter extends Target
{
    private $adaptee;

    public function __construct(Adaptee $adaptee)
    {
        $this->adaptee = $adaptee;
    }

    public function request(): string
    {
        return "Adapter: (TRANSLATED) " . strrev($this->adaptee->specificRequest());
    }
}

function clientCode(Target $target)
{
    echo $target->request();
}

echo "Client: I can work just fine with the Target objects:\n";
$target = new Target();
clientCode($target);

$adaptee = new Adaptee();
echo "Client: The Adaptee class has a weird interface. See, I don't understand it:\n";
echo "Adaptee: " . $adaptee->specificRequest();

echo "Client: But I can work with it via the Adapter:\n";
$adapter = new Adapter($adaptee);
clientCode($adapter);

output:

Client: I can work just fine with the Target objects:
Target: The default target's behavior.Client: The Adaptee class has a weird interface. See, I don't understand it:
Adaptee: .eetpadA eht fo roivaheb laicepSClient: But I can work with it via the Adapter:
Adapter: (TRANSLATED) Special behavior of the Adaptee.