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工厂方法模式(Factory Method)

1.3.1. 目的

对比简单工厂模式的优点是,您可以将其子类用不同的方法来创建一个对象。

举一个简单的例子,这个抽象类可能只是一个接口。

这种模式是「真正」的设计模式, 因为他实现了S.O.L.I.D原则中「D」的 「依赖倒置」。

这意味着工厂方法模式取决于抽象类,而不是具体的类。 这是与简单工厂模式和静态工厂模式相比的优势。

1.3.2. UML图

file

1.3.3. 代码

你可以在  GitHub 查看这段代码

FactoryMethod.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

abstract class FactoryMethod
{
    const CHEAP = 'cheap';
    const FAST = 'fast';

    abstract protected function createVehicle(string $type): VehicleInterface;

    public function create(string $type): VehicleInterface
    {
        $obj = $this->createVehicle($type);
        $obj->setColor('black');

        return $obj;
    }
}

ItalianFactory.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

class ItalianFactory extends FactoryMethod
{
    protected function createVehicle(string $type): VehicleInterface
    {
        switch ($type) {
            case parent::CHEAP:
                return new Bicycle();
            case parent::FAST:
                return new CarFerrari();
            default:
                throw new \InvalidArgumentException("$type is not a valid vehicle");
        }
    }
}

GermanFactory.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

class GermanFactory extends FactoryMethod
{
    protected function createVehicle(string $type): VehicleInterface
    {
        switch ($type) {
            case parent::CHEAP:
                return new Bicycle();
            case parent::FAST:
                $carMercedes = new CarMercedes();
                //  我们可以从已知的的类中找到具体的交通工具
                $carMercedes->addAMGTuning();

                return $carMercedes;
            default:
                throw new \InvalidArgumentException("$type is not a valid vehicle");
        }
    }
}

VehicleInterface.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

interface VehicleInterface
{
    public function setColor(string $rgb);
}

CarMercedes.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

class CarMercedes implements VehicleInterface
{
    /**
    * @var string
    */
    private $color;

    public function setColor(string $rgb)
    {
        $this->color = $rgb;
    }

    public function addAMGTuning()
    {
        // 在这里做额外的调整
    }
}

CarFerrari.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

class CarFerrari implements VehicleInterface
{
    /**
    * @var string
    */
    private $color;

    public function setColor(string $rgb)
    {
        $this->color = $rgb;
    }
}

Bicycle.php


<?php

namespace DesignPatterns\Creational\FactoryMethod;

class Bicycle implements VehicleInterface
{
    /**
    * @var string
    */
    private $color;

    public function setColor(string $rgb)
    {
        $this->color = $rgb;
    }
}

1.3.4. 测试

Tests/FactoryMethodTest.php


<?php

namespace DesignPatterns\Creational\FactoryMethod\Tests;

use DesignPatterns\Creational\FactoryMethod\Bicycle;
use DesignPatterns\Creational\FactoryMethod\CarFerrari;
use DesignPatterns\Creational\FactoryMethod\CarMercedes;
use DesignPatterns\Creational\FactoryMethod\FactoryMethod;
use DesignPatterns\Creational\FactoryMethod\GermanFactory;
use DesignPatterns\Creational\FactoryMethod\ItalianFactory;
use PHPUnit\Framework\TestCase;

class FactoryMethodTest extends TestCase
{
    public function testCanCreateCheapVehicleInGermany()
    {
        $factory = new GermanFactory();
        $result = $factory->create(FactoryMethod::CHEAP);

        $this->assertInstanceOf(Bicycle::class, $result);
    }

    public function testCanCreateFastVehicleInGermany()
    {
        $factory = new GermanFactory();
        $result = $factory->create(FactoryMethod::FAST);

        $this->assertInstanceOf(CarMercedes::class, $result);
    }

    public function testCanCreateCheapVehicleInItaly()
    {
        $factory = new ItalianFactory();
        $result = $factory->create(FactoryMethod::CHEAP);

        $this->assertInstanceOf(Bicycle::class, $result);
    }

    public function testCanCreateFastVehicleInItaly()
    {
        $factory = new ItalianFactory();
        $result = $factory->create(FactoryMethod::FAST);

        $this->assertInstanceOf(CarFerrari::class, $result);
    }

    /**
    * @expectedException \InvalidArgumentException
    * @expectedExceptionMessage spaceship is not a valid vehicle
    */
    public function testUnknownType()
    {
        (new ItalianFactory())->create('spaceship');
    }
}

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