3.10. State

3.10.1. Propósito

Encapsula el comportamiento variable de la misma rutina en función del estado de un objeto. Esta puede ser una forma más limpia para que un objeto cambie su comportamiento en tiempo de ejecución sin tener que recurrir a declaraciones condicionales monolíticas de gran tamaño

3.10.2. Diagrama UML

3.10.3. Código

Puedes encontrar el código en GitHub

ContextOrder.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class ContextOrder
{
    private StateOrder $state;

    public static function create(): ContextOrder
    {
        $order = new self();
        $order->state = new CreateOrder();

        return $order;
    }

    public function setState(StateOrder $state): void
    {
        $this->state = $state;
    }

    public function proceedToNext(): void
    {
        $this->state->proceedToNext($this);
    }

    public function toString(): string
    {
        return $this->state->toString();
    }
}

StateOrder.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

interface StateOrder
{
    public function proceedToNext(ContextOrder $context): void;

    public function toString(): string;
}

CreateOrder.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class CreateOrder implements StateOrder
{
    public function proceedToNext(ContextOrder $context): void
    {
        $context->setState(new ShippingOrder());
    }

    public function toString(): string
    {
        return 'created';
    }
}

ShippingOrder.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class ShippingOrder implements StateOrder
{
    public function proceedToNext(ContextOrder $context): void
    {
        $context->setState(new OrderDone());
    }

    public function toString(): string
    {
        return 'shipped';
    }
}

OrderDone.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class OrderDone implements StateOrder
{
    public function proceedToNext(ContextOrder $context): void
    {
        // there is nothing more to do
    }

    public function toString(): string
    {
        return 'done';
    }
}

3.10.4. Test

Tests/StateTest.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State\Tests;

use DesignPatterns\Behavioral\State\ContextOrder;
use PHPUnit\Framework\TestCase;

class StateTest extends TestCase
{
    public function testIsCreatedWithStateCreated(): void
    {
        $orderContext = ContextOrder::create();

        $this->assertSame('created', $orderContext->toString());
    }

    public function testCanProceedToStateShipped(): void
    {
        $contextOrder = ContextOrder::create();
        $contextOrder->proceedToNext();

        $this->assertSame('shipped', $contextOrder->toString());
    }

    public function testCanProceedToStateDone(): void
    {
        $contextOrder = ContextOrder::create();
        $contextOrder->proceedToNext();
        $contextOrder->proceedToNext();

        $this->assertSame('done', $contextOrder->toString());
    }

    public function testStateDoneIsTheLastPossibleState(): void
    {
        $contextOrder = ContextOrder::create();
        $contextOrder->proceedToNext();
        $contextOrder->proceedToNext();
        $contextOrder->proceedToNext();

        $this->assertSame('done', $contextOrder->toString());
    }
}