2.1. Adaptador / Wrapper

2.1.1. Propósito

Para traducir una interfaz para una clase en una interfaz compatible. Un adaptador permite que las clases que normalmente no podrían, trabajen juntas. Inicialmente no podrían debido a interfaces incompatibles al proporcionar su interfaz a los clientes durante el uso de la interfaz original.

2.1.2. Ejemplos

  • Adaptador de librerías DB Client

  • usar varios webservices y adaptadores diferentes normaliza los datos haciendo que la salida sea la misma para todos

2.1.3. Diagrama UML

Alt Adapter UML Diagram

2.1.4. Código

Puedes encontrar el código en GitHub

Book.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter;
 6
 7interface Book
 8{
 9    public function turnPage();
10
11    public function open();
12
13    public function getPage(): int;
14}

PaperBook.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter;
 6
 7class PaperBook implements Book
 8{
 9    private int $page;
10
11    public function open(): void
12    {
13        $this->page = 1;
14    }
15
16    public function turnPage(): void
17    {
18        $this->page++;
19    }
20
21    public function getPage(): int
22    {
23        return $this->page;
24    }
25}

EBook.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter;
 6
 7interface EBook
 8{
 9    public function unlock();
10
11    public function pressNext();
12
13    /**
14     * returns current page and total number of pages, like [10, 100] is page 10 of 100
15     *
16     * @return int[]
17     */
18    public function getPage(): array;
19}

EBookAdapter.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter;
 6
 7/**
 8 * This is the adapter here. Notice it implements Book,
 9 * therefore you don't have to change the code of the client which is using a Book
10 */
11class EBookAdapter implements Book
12{
13    public function __construct(protected EBook $eBook)
14    {
15    }
16
17    /**
18     * This class makes the proper translation from one interface to another.
19     */
20    public function open()
21    {
22        $this->eBook->unlock();
23    }
24
25    public function turnPage()
26    {
27        $this->eBook->pressNext();
28    }
29
30    /**
31     * notice the adapted behavior here: EBook::getPage() will return two integers, but Book
32     * supports only a current page getter, so we adapt the behavior here
33     */
34    public function getPage(): int
35    {
36        return $this->eBook->getPage()[0];
37    }
38}

Kindle.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter;
 6
 7/**
 8 * this is the adapted class. In production code, this could be a class from another package, some vendor code.
 9 * Notice that it uses another naming scheme and the implementation does something similar but in another way
10 */
11class Kindle implements EBook
12{
13    private int $page = 1;
14    private int $totalPages = 100;
15
16    public function pressNext()
17    {
18        $this->page++;
19    }
20
21    public function unlock()
22    {
23    }
24
25    /**
26     * returns current page and total number of pages, like [10, 100] is page 10 of 100
27     *
28     * @return int[]
29     */
30    public function getPage(): array
31    {
32        return [$this->page, $this->totalPages];
33    }
34}

2.1.5. Test

Tests/AdapterTest.php

 1<?php
 2
 3declare(strict_types=1);
 4
 5namespace DesignPatterns\Structural\Adapter\Tests;
 6
 7use DesignPatterns\Structural\Adapter\PaperBook;
 8use DesignPatterns\Structural\Adapter\EBookAdapter;
 9use DesignPatterns\Structural\Adapter\Kindle;
10use PHPUnit\Framework\TestCase;
11
12class AdapterTest extends TestCase
13{
14    public function testCanTurnPageOnBook()
15    {
16        $book = new PaperBook();
17        $book->open();
18        $book->turnPage();
19
20        $this->assertSame(2, $book->getPage());
21    }
22
23    public function testCanTurnPageOnKindleLikeInANormalBook()
24    {
25        $kindle = new Kindle();
26        $book = new EBookAdapter($kindle);
27
28        $book->open();
29        $book->turnPage();
30
31        $this->assertSame(2, $book->getPage());
32    }
33}