3.9. State

3.9.1. Purpose

Encapsulate varying behavior for the same routine based on an object’s state. This can be a cleaner way for an object to change its behavior at runtime without resorting to large monolithic conditional statements.

3.9.2. UML Diagram

Alt State UML Diagram

3.9.3. Code

You can also find this code on GitHub

ContextOrder.php

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<?php

namespace DesignPatterns\Behavioral\State;

class ContextOrder extends StateOrder
{
    public function getState():StateOrder
    {
        return static::$state;
    }

    public function setState(StateOrder $state)
    {
        static::$state = $state;
    }

    public function done()
    {
        static::$state->done();
    }

    public function getStatus(): string
    {
        return static::$state->getStatus();
    }
}

StateOrder.php

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<?php

namespace DesignPatterns\Behavioral\State;

abstract class StateOrder
{
    /**
     * @var array
     */
    private $details;

    /**
     * @var StateOrder $state
     */
    protected static $state;

    /**
     * @return mixed
     */
    abstract protected function done();

    protected function setStatus(string $status)
    {
        $this->details['status'] = $status;
        $this->details['updatedTime'] = time();
    }

    protected function getStatus(): string
    {
        return $this->details['status'];
    }
}

ShippingOrder.php

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<?php

namespace DesignPatterns\Behavioral\State;

class ShippingOrder extends StateOrder
{
    public function __construct()
    {
        $this->setStatus('shipping');
    }

    protected function done()
    {
        $this->setStatus('completed');
    }
}

CreateOrder.php

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<?php

namespace DesignPatterns\Behavioral\State;

class CreateOrder extends StateOrder
{
    public function __construct()
    {
        $this->setStatus('created');
    }

    protected function done()
    {
        static::$state = new ShippingOrder();
    }
}

3.9.4. Test

Tests/StateTest.php

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<?php

namespace DesignPatterns\Behavioral\State\Tests;

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

class StateTest extends TestCase
{
    public function testCanShipCreatedOrder()
    {
        $order = new CreateOrder();
        $contextOrder = new ContextOrder();
        $contextOrder->setState($order);
        $contextOrder->done();

        $this->assertEquals('shipping', $contextOrder->getStatus());
    }

    public function testCanCompleteShippedOrder()
    {
        $order = new CreateOrder();
        $contextOrder = new ContextOrder();
        $contextOrder->setState($order);
        $contextOrder->done();
        $contextOrder->done();

        $this->assertEquals('completed', $contextOrder->getStatus());
    }
}