1.9. Static Factory

1.9.1. Purpose

Similar to the AbstractFactory, this pattern is used to create series ofrelated or dependent objects. The difference between this and theabstract factory pattern is that the static factory pattern uses justone static method to create all types of objects it can create. It isusually named factory or build.

1.9.2. Examples

• Zend Framework: Zend_Cache_Backend or _Frontend use a factorymethod create cache backends or frontends

1.9.3. UML Diagram

1.9.4. Code

You can also find this code on GitHub

StaticFactory.php

<?php
 
namespace DesignPatterns\Creational\StaticFactory;
 
/**
 * 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
{
    /**
     * @param string $type
     *
     * @return FormatterInterface
     */
    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');
    }
}

FormatterInterface.php

<?php
 
namespace DesignPatterns\Creational\StaticFactory;
 
interface FormatterInterface
{
}

FormatString.php

<?php
 
namespace DesignPatterns\Creational\StaticFactory;
 
class FormatString implements FormatterInterface
{
}

FormatNumber.php

<?php
 
namespace DesignPatterns\Creational\StaticFactory;
 
class FormatNumber implements FormatterInterface
{
}

1.9.5. Test

Tests/StaticFactoryTest.php

<?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')
        );
    }
 
    /**
     * @expectedException \InvalidArgumentException
     */
    public function testException()
    {
        StaticFactory::factory('object');
    }
}