建造者模式（Builder）

1.2.1. 目的

建造者是创建一个复杂对象的一部分接口。

有时候，如果建造者对他所创建的东西拥有较好的知识储备，这个接口就可能成为一个有默认方法的抽象类（又称为适配器）。

如果对象有复杂的继承树，那么对于建造者来说，有一个复杂继承树也是符合逻辑的。

注意：建造者通常有一个「流式接口」，例如 PHPUnit 模拟生成器。

1.2.2. 例子

• PHPUnit: 模拟生成器

1.2.3. UML Diagram

1.2.4. 代码

你也可以在 GitHub 上找到这个代码。

Director.php

namespace DesignPatterns\Creational\Builder;

use DesignPatterns\Creational\Builder\Parts\Vehicle;

/**
 * Director 类是建造者模式的一部分。 它可以实现建造者模式的接口
 * 并在构建器的帮助下构建一个复杂的对象
 *
 * 您也可以注入许多构建器而不是构建更复杂的对象
 */
class Director
{
    public function build(BuilderInterface $builder): Vehicle
    {
        $builder->createVehicle();
        $builder->addDoors();
        $builder->addEngine();
        $builder->addWheel();

        return $builder->getVehicle();
    }
}

BuilderInterface.php

namespace DesignPatterns\Creational\Builder;

use DesignPatterns\Creational\Builder\Parts\Vehicle;

interface BuilderInterface
{
    public function createVehicle();

    public function addWheel();

    public function addEngine();

    public function addDoors();

    public function getVehicle(): Vehicle;
}

TruckBuilder.php

namespace DesignPatterns\Creational\Builder;

use DesignPatterns\Creational\Builder\Parts\Vehicle;

class TruckBuilder implements BuilderInterface
{
    /**
    * @var Parts\Truck
    */
    private $truck;

    public function addDoors()
    {
        $this->truck->setPart('rightDoor', new Parts\Door());
        $this->truck->setPart('leftDoor', new Parts\Door());
    }

    public function addEngine()
    {
        $this->truck->setPart('truckEngine', new Parts\Engine());
    }

    public function addWheel()
    {
        $this->truck->setPart('wheel1', new Parts\Wheel());
        $this->truck->setPart('wheel2', new Parts\Wheel());
        $this->truck->setPart('wheel3', new Parts\Wheel());
        $this->truck->setPart('wheel4', new Parts\Wheel());
        $this->truck->setPart('wheel5', new Parts\Wheel());
        $this->truck->setPart('wheel6', new Parts\Wheel());
    }

    public function createVehicle()
    {
        $this->truck = new Parts\Truck();
    }

    public function getVehicle(): Vehicle
    {
        return $this->truck;
    }
}

CarBuilder.php

namespace DesignPatterns\Creational\Builder;

use DesignPatterns\Creational\Builder\Parts\Vehicle;

class CarBuilder implements BuilderInterface
{
    /**
    * @var Parts\Car
    */
    private $car;

    public function addDoors()
    {
        $this->car->setPart('rightDoor', new Parts\Door());
        $this->car->setPart('leftDoor', new Parts\Door());
        $this->car->setPart('trunkLid', new Parts\Door());
    }

    public function addEngine()
    {
        $this->car->setPart('engine', new Parts\Engine());
    }

    public function addWheel()
    {
        $this->car->setPart('wheelLF', new Parts\Wheel());
        $this->car->setPart('wheelRF', new Parts\Wheel());
        $this->car->setPart('wheelLR', new Parts\Wheel());
        $this->car->setPart('wheelRR', new Parts\Wheel());
    }

    public function createVehicle()
    {
        $this->car = new Parts\Car();
    }

    public function getVehicle(): Vehicle
    {
        return $this->car;
    }
}

Parts/Vehicle.php

namespace DesignPatterns\Creational\Builder\Parts;

abstract class Vehicle
{
    /**
    * @var object[]
    */
    private $data = [];

    /**
    * @param string $key
    * @param object $value
    */
    public function setPart($key, $value)
    {
        $this->data[$key] = $value;
    }
}

Parts/Truck.php

namespace DesignPatterns\Creational\Builder\Parts;

class Truck extends Vehicle
{
}

Parts/Car.php

namespace DesignPatterns\Creational\Builder\Parts;

class Car extends Vehicle
{
}

Parts/Engine.php

namespace DesignPatterns\Creational\Builder\Parts;

class Engine
{
}

Parts/Wheel.php

namespace DesignPatterns\Creational\Builder\Parts;

class Wheel
{
}

Parts/Door.php

namespace DesignPatterns\Creational\Builder\Parts;

class Door
{
}

1.2.5. 测试

Tests/DirectorTest.php

namespace DesignPatterns\Creational\Builder\Tests;

use DesignPatterns\Creational\Builder\Parts\Car;
use DesignPatterns\Creational\Builder\Parts\Truck;
use DesignPatterns\Creational\Builder\TruckBuilder;
use DesignPatterns\Creational\Builder\CarBuilder;
use DesignPatterns\Creational\Builder\Director;
use PHPUnit\Framework\TestCase;

class DirectorTest extends TestCase
{
    public function testCanBuildTruck()
    {
        $truckBuilder = new TruckBuilder();
        $newVehicle = (new Director())->build($truckBuilder);

        $this->assertInstanceOf(Truck::class, $newVehicle);
    }

    public function testCanBuildCar()
    {
        $carBuilder = new CarBuilder();
        $newVehicle = (new Director())->build($carBuilder);

        $this->assertInstanceOf(Car::class, $newVehicle);
    }
}