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

OrderContext.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class OrderContext
{
    private State $state;

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

        return $order;
    }

    public function setState(State $state)
    {
        $this->state = $state;
    }

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

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

State.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

interface State
{
    public function proceedToNext(OrderContext $context);

    public function toString(): string;
}

StateCreated.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class StateCreated implements State
{
    public function proceedToNext(OrderContext $context)
    {
        $context->setState(new StateShipped());
    }

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

StateShipped.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class StateShipped implements State
{
    public function proceedToNext(OrderContext $context)
    {
        $context->setState(new StateDone());
    }

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

StateDone.php

<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\State;

class StateDone implements State
{
    public function proceedToNext(OrderContext $context)
    {
        // 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\OrderContext;
use PHPUnit\Framework\TestCase;

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

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

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

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

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

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

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

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