浅谈PHP设计模式之对象池模式Pool

在初始化实例成本高，实例化率高，可用实例不足的情况下，对象池可以极大地提升性能。在创建对象（尤其是通过网络）时间花销不确定的情况下，通过对象池在可期时间内就可以获得所需的对象。

无论如何，对象池模式在需要耗时创建对象方面，例如创建数据库连接，套接字连接，线程和大型图形对象（比方字体或位图等），使用起来都是大有裨益的。在某些情况下，简单的对象池（无外部资源，只占内存）可能效率不高，甚至会有损性能。

WorkerPool.php

<?phpnamespace DesignPatternsCreationalPool;class WorkerPool implements Countable{ /** * @var StringReverseWorker[] */ private $occupiedWorkers = []; /** * @var StringReverseWorker[] */ private $freeWorkers = []; public function get(): StringReverseWorker {if (count($this->freeWorkers) == 0) { $worker = new StringReverseWorker();} else { $worker = array_pop($this->freeWorkers);}$this->occupiedWorkers[spl_object_hash($worker)] = $worker;return $worker; } public function dispose(StringReverseWorker $worker) {$key = spl_object_hash($worker);if (isset($this->occupiedWorkers[$key])) { unset($this->occupiedWorkers[$key]); $this->freeWorkers[$key] = $worker;} } public function count(): int {return count($this->occupiedWorkers) + count($this->freeWorkers); }}

StringReverseWorker.php

<?phpnamespace DesignPatternsCreationalPool;class StringReverseWorker{ /** * @var DateTime */ private $createdAt; public function __construct() {$this->createdAt = new DateTime(); } public function run(string $text) {return strrev($text); }}测试

Tests/PoolTest.php

<?phpnamespace DesignPatternsCreationalPoolTests;use DesignPatternsCreationalPoolWorkerPool;use PHPUnitFrameworkTestCase;class PoolTest extends TestCase{ public function testCanGetNewInstancesWithGet() {$pool = new WorkerPool();$worker1 = $pool->get();$worker2 = $pool->get();$this->assertCount(2, $pool);$this->assertNotSame($worker1, $worker2); } public function testCanGetSameInstanceTwiceWhenDisposingItFirst() {$pool = new WorkerPool();$worker1 = $pool->get();$pool->dispose($worker1);$worker2 = $pool->get();$this->assertCount(1, $pool);$this->assertSame($worker1, $worker2); }}

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