3.11. Strategy

3.11.1. Terminology:

  • Context (Bağlam)
  • Strategy (Yordam)
  • Concrete Strategy (Somut Yordam)

3.11.2. Amaç

Yordamları ayırarak, aralarındaki hızlı geçişlere olanak sağlamak. Aynı zamanda bu desen, kalıtım (inheritance) için iyi bir alternatiftir (genişletilmiş soyut bir sınıf sahibi olmak yerine).

3.11.3. Örnekler

  • sorting a list of objects, one strategy by date, the other by id
  • simplify unit testing: e.g. switching between file and in-memory storage

3.11.4. UML Diyagramı

Alt Strategy UML Diagram

3.11.5. Kod

Bu kodu Github üzerinde de bulabilirsiniz.

Context.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Strategy;

class Context
{
    public function __construct(private Comparator $comparator)
    {
    }

    public function executeStrategy(array $elements): array
    {
        uasort($elements, [$this->comparator, 'compare']);

        return $elements;
    }
}

Comparator.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Strategy;

interface Comparator
{
    /**
     * @param mixed $a
     * @param mixed $b
     */
    public function compare($a, $b): int;
}

DateComparator.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Strategy;

use DateTime;

class DateComparator implements Comparator
{
    public function compare($a, $b): int
    {
        $aDate = new DateTime($a['date']);
        $bDate = new DateTime($b['date']);

        return $aDate <=> $bDate;
    }
}

IdComparator.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Strategy;

class IdComparator implements Comparator
{
    public function compare($a, $b): int
    {
        return $a['id'] <=> $b['id'];
    }
}

3.11.6. Test

Tests/StrategyTest.php

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<?php

declare(strict_types=1);

namespace DesignPatterns\Behavioral\Strategy\Tests;

use DesignPatterns\Behavioral\Strategy\Context;
use DesignPatterns\Behavioral\Strategy\DateComparator;
use DesignPatterns\Behavioral\Strategy\IdComparator;
use PHPUnit\Framework\TestCase;

class StrategyTest extends TestCase
{
    public function provideIntegers()
    {
        return [
            [
                [['id' => 2], ['id' => 1], ['id' => 3]],
                ['id' => 1],
            ],
            [
                [['id' => 3], ['id' => 2], ['id' => 1]],
                ['id' => 1],
            ],
        ];
    }

    public function provideDates()
    {
        return [
            [
                [['date' => '2014-03-03'], ['date' => '2015-03-02'], ['date' => '2013-03-01']],
                ['date' => '2013-03-01'],
            ],
            [
                [['date' => '2014-02-03'], ['date' => '2013-02-01'], ['date' => '2015-02-02']],
                ['date' => '2013-02-01'],
            ],
        ];
    }

    /**
     * @dataProvider provideIntegers
     *
     * @param array $collection
     * @param array $expected
     */
    public function testIdComparator($collection, $expected)
    {
        $obj = new Context(new IdComparator());
        $elements = $obj->executeStrategy($collection);

        $firstElement = array_shift($elements);
        $this->assertSame($expected, $firstElement);
    }

    /**
     * @dataProvider provideDates
     *
     * @param array $collection
     * @param array $expected
     */
    public function testDateComparator($collection, $expected)
    {
        $obj = new Context(new DateComparator());
        $elements = $obj->executeStrategy($collection);

        $firstElement = array_shift($elements);
        $this->assertSame($expected, $firstElement);
    }
}