PHP 適配器模式

目的

將某個類的接口轉(zhuǎn)換成與另一個接口兼容。適配器通過將原始接口進(jìn)行轉(zhuǎn)換，給用戶提供一個兼容接口，使得原來因為接口不同而無法一起使用的類可以得到兼容。

例子

• 數(shù)據(jù)庫客戶端庫適配器
• 使用不同的webservices，通過適配器來標(biāo)準(zhǔn)化輸出數(shù)據(jù)，從而保證不同webservice輸出的數(shù)據(jù)是一致的

UML 圖

2.1.4. 代碼

Book.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter;

interface Book
{
    public function turnPage();

    public function open();

    public function getPage(): int;
}

PaperBook.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter;

class PaperBook implements Book
{
    private int $page;

    public function open(): void
    {
        $this->page = 1;
    }

    public function turnPage(): void
    {
        $this->page++;
    }

    public function getPage(): int
    {
        return $this->page;
    }
}

EBook.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter;

interface EBook
{
    public function unlock();

    public function pressNext();

    /**
     * returns current page and total number of pages, like [10, 100] is page 10 of 100
     *
     * @return int[]
     */
    public function getPage(): array;
}

EBookAdapter.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter;

/**
 * This is the adapter here. Notice it implements Book,
 * therefore you don't have to change the code of the client which is using a Book
 */
class EBookAdapter implements Book
{
    public function __construct(protected EBook $eBook)
    {
    }

    /**
     * This class makes the proper translation from one interface to another.
     */
    public function open()
    {
        $this->eBook->unlock();
    }

    public function turnPage()
    {
        $this->eBook->pressNext();
    }

    /**
     * notice the adapted behavior here: EBook::getPage() will return two integers, but Book
     * supports only a current page getter, so we adapt the behavior here
     */
    public function getPage(): int
    {
        return $this->eBook->getPage()[0];
    }
}

Kindle.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter;

/**
 * this is the adapted class. In production code, this could be a class from another package, some vendor code.
 * Notice that it uses another naming scheme and the implementation does something similar but in another way
 */
class Kindle implements EBook
{
    private int $page = 1;
    private int $totalPages = 100;

    public function pressNext()
    {
        $this->page++;
    }

    public function unlock()
    {
    }

    /**
     * returns current page and total number of pages, like [10, 100] is page 10 of 100
     *
     * @return int[]
     */
    public function getPage(): array
    {
        return [$this->page, $this->totalPages];
    }
}

測試

Tests/AdapterTest.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Structural\Adapter\Tests;

use DesignPatterns\Structural\Adapter\PaperBook;
use DesignPatterns\Structural\Adapter\EBookAdapter;
use DesignPatterns\Structural\Adapter\Kindle;
use PHPUnit\Framework\TestCase;

class AdapterTest extends TestCase
{
    public function testCanTurnPageOnBook()
    {
        $book = new PaperBook();
        $book->open();
        $book->turnPage();

        $this->assertSame(2, $book->getPage());
    }

    public function testCanTurnPageOnKindleLikeInANormalBook()
    {
        $kindle = new Kindle();
        $book = new EBookAdapter($kindle);

        $book->open();
        $book->turnPage();

        $this->assertSame(2, $book->getPage());
    }
}