分离「策略」并使他们之间能互相快速切换。此外,这种模式是一种不错的继承替代方案(替代使用扩展抽象类的方式)。php
简化版的的单元测试:例如,在使用文件存储和内存存储之间互相切换laravel
对一个对象列表进行排序,一种按照日期,一种按照 id面试
<?php namespace DesignPatterns\Behavioral\Strategy; class Context { /** * @var ComparatorInterface */ private $comparator; public function __construct(ComparatorInterface $comparator) { $this->comparator = $comparator; } public function executeStrategy(array $elements) : array { uasort($elements, [$this->comparator, 'compare']); return $elements; } }
<?php namespace DesignPatterns\Behavioral\Strategy; interface ComparatorInterface { /** * @param mixed $a * @param mixed $b * * @return int */ public function compare($a, $b): int; }
<?php namespace DesignPatterns\Behavioral\Strategy; class DateComparator implements ComparatorInterface { /** * @param mixed $a * @param mixed $b * * @return int */ public function compare($a, $b): int { $aDate = new \DateTime($a['date']); $bDate = new \DateTime($b['date']); return $aDate <=> $bDate; } }
<?php namespace DesignPatterns\Behavioral\Strategy; class IdComparator implements ComparatorInterface { /** * @param mixed $a * @param mixed $b * * @return int */ public function compare($a, $b): int { return $a['id'] <=> $b['id']; } }
<?php 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); $this->assertEquals($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); $this->assertEquals($expected, $firstElement); } }
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