工厂方法模式
目的
与简单工厂模式相比，工厂方法模式的优点是你可以通过子类来实现不同的对象创建方式。
对于简单的情况，这个抽象类可以只是一个接口。
这种模式是一种“真正的”设计模式，因为它实现了依赖倒置原则，也就是 SOLID 原则中的 D。
这意味着 FactoryMethod 类依赖于抽象，而不是具体的类。与简单工厂模式或静态工厂模式相比，这才是真正的技巧。
UML 类图
代码
Logger.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
interface Logger
{
public function log(string $message);
}
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StdoutLogger.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
class StdoutLogger implements Logger
{
public function log(string $message)
{
echo $message;
}
}
|
FileLogger.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
class FileLogger implements Logger
{
private string $filePath;
public function __construct(string $filePath)
{
$this->filePath = $filePath;
}
public function log(string $message)
{
file_put_contents($this->filePath, $message . PHP_EOL, FILE_APPEND);
}
}
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LoggerFactory.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
interface LoggerFactory
{
public function createLogger(): Logger;
}
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StdoutLoggerFactory.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
class StdoutLoggerFactory implements LoggerFactory
{
public function createLogger(): Logger
{
return new StdoutLogger();
}
}
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FileLoggerFactory
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod;
class FileLoggerFactory implements LoggerFactory
{
private string $filePath;
public function __construct(string $filePath)
{
$this->filePath = $filePath;
}
public function createLogger(): Logger
{
return new FileLogger($this->filePath);
}
}
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测试
Tests/FactoryMethodTest.php
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| <?php declare(strict_types = 1);
namespace DesignPatterns\Creational\FactoryMethod\Tests;
use DesignPatterns\Creational\FactoryMethod\FileLogger;
use DesignPatterns\Creational\FactoryMethod\FileLoggerFactory;
use DesignPatterns\Creational\FactoryMethod\StdoutLogger;
use DesignPatterns\Creational\FactoryMethod\StdoutLoggerFactory;
use PHPUnit\Framework\TestCase;
class FactoryMethodTest extends TestCase
{
public function testCanCreateStdoutLogging()
{
$loggerFactory = new StdoutLoggerFactory();
$logger = $loggerFactory->createLogger();
$this->assertInstanceOf(StdoutLogger::class, $logger);
}
public function testCanCreateFileLogging()
{
$loggerFactory = new FileLoggerFactory(sys_get_temp_dir());
$logger = $loggerFactory->createLogger();
$this->assertInstanceOf(FileLogger::class, $logger);
}
}
|
