1.2. Budowniczy (Builder)

1.2.1. Przeznaczenie

Wzorzec Budowniczego pozwala na podział skomplikowanego procesu tworzenia obiektu, na kilka mniejszych etapów, gdzie każdy z nich może być implementowany na różne sposoby. Budowniczy jest interfejsem, który pozwala budować części takiego obiektu.

Jeżeli Budowniczy ma najlepszą wiedzę na temat tworzonego obiektu, wtedy zamiast interfejsu można zastosować klasę abstrakcyjną z domyślnymi metodami (patrz Adapter).

Jeżeli struktura dziedziczenia poszczególnych klas jest rozbudowana, wtedy struktura dziedziczenia Budowniczych powinna temu odpowiadać.

Budowniczy często wykorzystuje płynny interfejs (ang. fluent interface) jak na przykład Mock Builder z biblioteki PHPUnit.

1.2.2. Przykłady

• PHPUnit: Mock Builder

1.2.3. Diagram UML

1.2.4. Kod

Ten kod znajdziesz również na GitHub.

Director.php

<?php

namespace DesignPatterns\Creational\Builder;

use DesignPatterns\Creational\Builder\Parts\Vehicle;

/**
 * Director is part of the builder pattern. It knows the interface of the builder
 * and builds a complex object with the help of the builder
 *
 * You can also inject many builders instead of one to build more complex objects
 */
class Director
{
    public function build(BuilderInterface $builder): Vehicle
    {
        $builder->createVehicle();
        $builder->addDoors();
        $builder->addEngine();
        $builder->addWheel();

        return $builder->getVehicle();
    }
}

BuilderInterface.php

<?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

<?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

<?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

<?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

<?php

namespace DesignPatterns\Creational\Builder\Parts;

class Truck extends Vehicle
{
}

Parts/Car.php

<?php

namespace DesignPatterns\Creational\Builder\Parts;

class Car extends Vehicle
{
}

Parts/Engine.php

<?php

namespace DesignPatterns\Creational\Builder\Parts;

class Engine
{
}

Parts/Wheel.php

<?php

namespace DesignPatterns\Creational\Builder\Parts;

class Wheel
{
}

Parts/Door.php

<?php

namespace DesignPatterns\Creational\Builder\Parts;

class Door
{
}

1.2.5. Testy

Tests/DirectorTest.php

<?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);
    }
}