静态工厂

与简单工厂比较而言，优先使用 简单工厂模式！

<?php
namespace DesignPatterns\Creational\StaticFactory;

final class StaticFactory
{
    public static function factory(string $type): FormatterInterface
    {
        if ($type == 'number') {
            return new FormatNumber();
        }

        if ($type == 'string') {
            return new FormatString();
        }

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

<?php
namespace DesignPatterns\Creational\StaticFactory;

interface FormatterInterface
{
}

<?php
namespace DesignPatterns\Creational\StaticFactory;

class FormatString implements FormatterInterface
{
}

<?php
namespace DesignPatterns\Creational\StaticFactory;

class FormatNumber implements FormatterInterface
{
}

<?php

namespace DesignPatterns\Creational\StaticFactory\Tests;

use DesignPatterns\Creational\StaticFactory\StaticFactory;
use PHPUnit\Framework\TestCase;

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

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

    public function testException()
    {
        StaticFactory::factory('object');
    }
}