Стратегия (англ. Strategy) — поведенческий шаблон проектирования, предназначенный для определения семейства алгоритмов, инкапсуляции каждого из них и обеспечения их взаимозаменяемости. Это позволяет выбирать алгоритм путём определения соответствующего класса. Шаблон Strategy позволяет менять выбранный алгоритм независимо от объектов-клиентов, которые его используют.

• Strategies
  • AddStrategy.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\Strategy\Strategies;
    
    /**
     * Class AddStrategy
     * @package DesignPatterns\Behavioral\Strategy\Strategies
     */
    class AddStrategy implements StrategyInterface
    {
        /**
         * @param int $x
         * @param int $y
         *
         * @return int
         */
        public function algorithm(int $x, int $y): int
        {
            return $x + $y;
        }
    }
    
                  

  • MultiplyStrategy.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\Strategy\Strategies;
    
    /**
     * Class MultiplyStrategy
     * @package DesignPatterns\Behavioral\Strategy\Strategies
     */
    class MultiplyStrategy implements StrategyInterface
    {
        /**
         * @param int $x
         * @param int $y
         *
         * @return int
         */
        public function algorithm(int $x, int $y): int
        {
            return $x * $y;
        }
    }
    
                  

  • StrategyInterface.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\Strategy\Strategies;
    
    /**
     * Interface StrategyInterface
     * @package DesignPatterns\Behavioral\Strategy\Strategies
     */
    interface StrategyInterface
    {
        /**
         * @param int $x
         * @param int $y
         *
         * @return int
         */
        public function algorithm(int $x, int $y): int;
    }
    
                  

  • SubtractStrategy.php

                  
    <?php
    
    namespace DesignPatterns\Behavioral\Strategy\Strategies;
    
    /**
     * Class SubtractStrategy
     * @package DesignPatterns\Behavioral\Strategy\Strategies
     */
    class SubtractStrategy implements StrategyInterface
    {
        /**
         * @param int $x
         * @param int $y
         *
         * @return int
         */
        public function algorithm(int $x, int $y): int
        {
            return $x - $y;
        }
    }
    
                  

• SimpleCalculator.php

                
  <?php
  
  namespace DesignPatterns\Behavioral\Strategy;
  
  use DesignPatterns\Behavioral\Strategy\Strategies\StrategyInterface;
  
  /**
   * Class SimpleCalculator
   * @package DesignPatterns\Behavioral\Strategy
   */
  class SimpleCalculator
  {
      /**
       * @var int
       */
      private $x;
  
      /**
       * @var int
       */
      private $y;
  
      /**
       * @var StrategyInterface
       */
      private $strategy;
  
      /**
       * SimpleCalculator constructor.
       *
       * @param int $x
       * @param int $y
       */
      public function __construct(int $x, int $y)
      {
          $this->x = $x;
          $this->y = $y;
      }
  
      /**
       * @param StrategyInterface $strategy
       *
       * @return void
       */
      public function setStrategy(StrategyInterface $strategy)
      {
          $this->strategy = $strategy;
      }
  
      /**
       * @return int
       */
      public function execute(): int
      {
          return $this->strategy->algorithm($this->x, $this->y);
      }
  }
  
                

Test case:

StrategyTest.php

  
<?php

namespace DesignPatterns\Tests\Behavioral\Strategy;

use DesignPatterns\Behavioral\Strategy\SimpleCalculator;
use DesignPatterns\Behavioral\Strategy\Strategies\AddStrategy;
use DesignPatterns\Behavioral\Strategy\Strategies\MultiplyStrategy;
use DesignPatterns\Behavioral\Strategy\Strategies\SubtractStrategy;
use PHPUnit_Framework_TestCase;

class StrategyTest extends PHPUnit_Framework_TestCase
{
    public function provideIntegersForAdd()
    {
        return [
            [2, 3, 5],
            [8, 3, 11],
            [-3, 5, 2],
            [23, -3, 20],
            [-42, -20, -62],
        ];
    }

    public function provideIntegersForSub()
    {
        return [
            [2, 3, -1],
            [8, 3, 5],
            [-3, 5, -8],
            [23, -3, 26],
            [-42, -20, -22],
        ];
    }

    public function provideIntegersForMulti()
    {
        return [
            [2, 3, 6],
            [8, 3, 24],
            [-3, 5, -15],
            [23, -3, -69],
            [-42, -20, 840],
        ];
    }

    /**
     * @dataProvider provideIntegersForAdd
     *
     * @param int $x
     * @param int $y
     * @param int $expected
     */
    public function testSimpleCalculatorWithAddStrategy(int $x, int $y, int $expected)
    {
        $simpleCalculator = new SimpleCalculator($x, $y);
        $simpleCalculator->setStrategy(new AddStrategy());

        $this->assertEquals($expected, $simpleCalculator->execute());
    }

    /**
     * @dataProvider provideIntegersForSub
     *
     * @param int $x
     * @param int $y
     * @param int $expected
     */
    public function testSimpleCalculatorWithSubtractStrategy(int $x, int $y, int $expected)
    {
        $simpleCalculator = new SimpleCalculator($x, $y);
        $simpleCalculator->setStrategy(new SubtractStrategy());

        $this->assertEquals($expected, $simpleCalculator->execute());
    }

    /**
     * @dataProvider provideIntegersForMulti
     *
     * @param int $x
     * @param int $y
     * @param int $expected
     */
    public function testSimpleCalculatorWithMultiplyStrategy(int $x, int $y, int $expected)
    {
        $simpleCalculator = new SimpleCalculator($x, $y);
        $simpleCalculator->setStrategy(new MultiplyStrategy());

        $this->assertEquals($expected, $simpleCalculator->execute());
    }
}