3.10. State

3.10.1. Amaç

Bir nesnenin durumuna bağlı olarak aynı yordam (routine) için değişen davranışları sarmalar. Bu, bir nesnenin davranışını büyük bölüntüsüz koşullu ifadelere (monolithic conditional statements) başvurmadan koşum anında (runtime) değiştirmenin daha temiz bir yolu olabilir.

3.10.2. UML Diyagramı

3.10.3. Kod

Bu kodu Github üzerinde de bulabilirsiniz.

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());
    }
}