1. 设计模式
  2. 结构型模式
  3. 桥接模式

桥接模式

目的

将抽象与实现解耦，使两者可以独立变化。

UML 类图

桥接模式类图

代码

Formatter.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

interface Formatter
{
    public function format(string $text): string;
}

PlainTextFormatter.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

class PlainTextFormatter implements Formatter
{
    public function format(string $text): string
    {
        return $text;
    }
}

HtmlFormatter.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

class HtmlFormatter implements Formatter
{
    public function format(string $text): string
    {
        return sprintf('<p>%s</p>', $text);
    }
}

Service.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

abstract class Service
{
    protected Formatter $implementation;

    public function __construct(Formatter $printer)
    {
        $this->implementation = $printer;
    }

    public function setImplementation(Formatter $printer)
    {
        $this->implementation = $printer;
    }

    abstract public function get(): string;
}

HelloWorldService.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

class HelloWorldService extends Service
{
    public function get(): string
    {
        return $this->implementation->format('Hello World');
    }
}

PingService.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge;

class PingService extends Service
{
    public function get(): string
    {
        return $this->implementation->format('pong');
    }
}

测试

Tests/BridgeTest.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Structural\Bridge\Tests;

use DesignPatterns\Structural\Bridge\HelloWorldService;
use DesignPatterns\Structural\Bridge\HtmlFormatter;
use DesignPatterns\Structural\Bridge\PlainTextFormatter;
use PHPUnit\Framework\TestCase;

class BridgeTest extends TestCase
{
    public function testCanPrintUsingThePlainTextFormatter()
    {
        $service = new HelloWorldService(new PlainTextFormatter());

        $this->assertSame('Hello World', $service->get());
    }

    public function testCanPrintUsingTheHtmlFormatter()
    {
        $service = new HelloWorldService(new HtmlFormatter());

        $this->assertSame('<p>Hello World</p>', $service->get());
    }
}
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