1.8. 静态工厂

1.8.1. 目的

和抽象工厂类似，静态工厂模式用来创建一系列互相关联或依赖的对象，和抽象工厂模式不同的是静态工厂模式只用一个静态方法就解决了所有类型的对象创建，通常被命名为``工厂`` 或者 构建器

1.8.2. UML 图

Alt StaticFactory UML Diagram

1.8.3. 代码

你可以在 GitHub 上找到这些代码

StaticFactory.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\StaticFactory;

use InvalidArgumentException;

/**
 * Note1: Remember, static means global state which is evil because it can't be mocked for tests
 * Note2: Cannot be subclassed or mock-upped or have multiple different instances.
 */
final class StaticFactory
{
    public static function factory(string $type): Formatter
    {
        if ($type == 'number') {
            return new FormatNumber();
        } elseif ($type == 'string') {
            return new FormatString();
        }

        throw new InvalidArgumentException('Unknown format given');
    }
}

Formatter.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\StaticFactory;

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

FormatString.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\StaticFactory;

class FormatString implements Formatter
{
    public function format(string $input): string
    {
        return $input;
    }
}

FormatNumber.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\StaticFactory;

class FormatNumber implements Formatter
{
    public function format(string $input): string
    {
        return number_format((int) $input);
    }
}

1.8.4. 测试

Tests/StaticFactoryTest.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\StaticFactory\Tests;

use InvalidArgumentException;
use DesignPatterns\Creational\StaticFactory\FormatNumber;
use DesignPatterns\Creational\StaticFactory\FormatString;
use DesignPatterns\Creational\StaticFactory\StaticFactory;
use PHPUnit\Framework\TestCase;

class StaticFactoryTest extends TestCase
{
    public function testCanCreateNumberFormatter()
    {
        $this->assertInstanceOf(FormatNumber::class, StaticFactory::factory('number'));
    }

    public function testCanCreateStringFormatter()
    {
        $this->assertInstanceOf(FormatString::class, StaticFactory::factory('string'));
    }

    public function testException()
    {
        $this->expectException(InvalidArgumentException::class);

        StaticFactory::factory('object');
    }
}