Состояние (англ. State) — поведенческий шаблон проектирования. Инкапсулирует изменение поведения одних и тех же методов в зависимости от состояния объекта. Этот шаблон поможет изящным способом изменить поведение объекта во время выполнения, не прибегая к большим монолитным условным операторам. Извне создаётся впечатление, что изменился класс объекта.

• States
  • AbstractState.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\State\States;
    
    use DesignPatterns\Behavioral\State\Glass;
    use Exception;
    
    /**
     * Class AbstractState
     * @package DesignPatterns\Behavioral\State\States
     */
    abstract class AbstractState implements StateInterface
    {
        const STATE = null;
    
        /**
         * @var Glass
         */
        protected $glass;
    
        /**
         * AbstractState constructor.
         *
         * @param Glass $glass
         */
        public function __construct(Glass $glass)
        {
            $this->glass = $glass;
        }
    
        /**
         * @return string
         */
        protected function getGlassState(): string
        {
            $glassState = $this->glass->getState();
    
            return $glassState::STATE;
        }
    
        /**
         * @return FillState
         *
         * @throws Exception
         */
        abstract public function onFilled(): FillState;
    
        /**
         * @return EmptyState
         *
         * @throws Exception
         */
        abstract public function onEmpty(): EmptyState;
    }
    
                  

  • EmptyState.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\State\States;
    
    use Exception;
    
    /**
     * Class EmptyState
     * @package DesignPatterns\Behavioral\State\States
     */
    class EmptyState extends AbstractState
    {
        const STATE = 'Empty';
    
        /**
         * @return FillState
         *
         * @throws Exception
         */
        public function onFilled(): FillState
        {
            if (static::STATE === $this->getGlassState()) {
                return new FillState($this->glass);
            }
    
            throw new Exception('Can\'t to fill filled glass.');
        }
    
        /**
         * @return EmptyState
         *
         * @throws Exception
         */
        public function onEmpty(): EmptyState
        {
            throw new Exception('Сan\'t pour the empty glass.');
        }
    }
    
                  

  • FillState.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\State\States;
    
    use Exception;
    
    /**
     * Class FillState
     * @package DesignPatterns\Behavioral\State\States
     */
    class FillState extends AbstractState
    {
        const STATE = 'Fill';
    
        /**
         * @throws Exception
         */
        public function onFilled(): FillState
        {
            throw new Exception('Can\'t to fill filled glass.');
        }
    
        /**
         * @return EmptyState
         *
         * @throws Exception
         */
        public function onEmpty(): EmptyState
        {
            if (static::STATE === $this->getGlassState()) {
                return new EmptyState($this->glass);
            }
    
            throw new Exception('Сan\'t pour the empty glass.');
        }
    }
    
                  

  • StateInterface.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\State\States;
    
    use DesignPatterns\Behavioral\State\Glass;
    
    /**
     * Interface StateInterface
     * @package DesignPatterns\Behavioral\State\States
     */
    interface StateInterface
    {
        /**
         * StateInterface constructor.
         *
         * @param Glass $glass
         */
        public function __construct(Glass $glass);
    
        /**
         * @return FillState
         */
        public function onFilled(): FillState;
    
        /**
         * @return EmptyState
         */
        public function onEmpty(): EmptyState;
    }
    
                  

• Glass.php

                
  <?php
  
  namespace DesignPatterns\Behavioral\State;
  
  use DesignPatterns\Behavioral\State\States\EmptyState;
  
  class Glass
  {
      protected $state;
  
      public function __construct()
      {
          $this->state = new EmptyState($this);
      }
  
      public function fill()
      {
          $this->state = $this->state->onFilled();
      }
      public function pour()
      {
          $this->state = $this->state->onEmpty();
      }
  
      public function getState()
      {
          return $this->state;
      }
  }
  
                

Test case:

StateTest.php

  
<?php

namespace DesignPatterns\Tests\Behavioral\State;

use DesignPatterns\Behavioral\State\Glass;
use Exception;
use PHPUnit_Framework_TestCase;

class StateTest extends PHPUnit_Framework_TestCase
{
    public function testTryGlassInit()
    {
        $glass = new Glass();
        $this->assertInstanceOf('DesignPatterns\Behavioral\State\States\EmptyState', $glass->getState());

        $someGlass = new Glass();
        $this->assertNotInstanceOf('DesignPatterns\Behavioral\State\States\FillState', $someGlass->getState());
    }

    public function testTryFillGlass()
    {
        $glass = new Glass();
        $glass->fill();
        $this->assertInstanceOf('DesignPatterns\Behavioral\State\States\FillState', $glass->getState());

        $glass->pour();
        $glass->fill();
        $this->assertInstanceOf('DesignPatterns\Behavioral\State\States\FillState', $glass->getState());
    }

    public function testTryPourGlass()
    {
        $glass = new Glass();
        $glass->fill();
        $glass->pour();
        $this->assertInstanceOf('DesignPatterns\Behavioral\State\States\EmptyState', $glass->getState());

        $glass->fill();
        $glass->pour();
        $this->assertInstanceOf('DesignPatterns\Behavioral\State\States\EmptyState', $glass->getState());
    }

    public function testExceptionTryFillFilledGlass()
    {
        $this->expectException(Exception::class);
        $glass = new Glass();
        $glass->fill();
        $glass->fill();
    }

    public function testExceptionTryPourTheEmptyGlass()
    {
        $this->expectException(Exception::class);
        $glass = new Glass();
        $glass->pour();
    }
}