PHP设计模式系列（二十一）：享元模式

享元模式

享元模式(Flyweight Pattern)：运用共享技术有效地支持大量细粒度对象的复用。系统只使用少量的对象，而这些对象都很相似，状态变化很小，可以实现对象的多次复用。由于享元模式要求能够共享的对象必须是细粒度对象，因此它又称为轻量级模式，它是一种对象结构型模式。

模式结构

享元模式包含如下角色：

• Flyweight: 抽象享元类
• ConcreteFlyweight: 具体享元类
• UnsharedConcreteFlyweight: 非共享具体享元类
• FlyweightFactory: 享元工厂类

结构图

PHP代码实现

<?php/** * 享元模式 */abstract class Flyweight {    abstract public function operation($state);}//具体享元角色class ConcreteFlyweight extends Flyweight {    private $state = null;    public function __construct($state) {        $this->state = $state;    }    public function operation($state) {        var_dump('具体Flyweight:'.$state);    }}//不共享的具体享元，客户端直接调用class UnsharedConcreteFlyweight extends Flyweight {    private $state = null;    public function __construct($state) {        $this->state = $state;    }    public function operation($state) {        var_dump('不共享的具体Flyweight:'.$state);    }}//享元工厂角色class FlyweightFactory {    private $flyweights;    public function __construct() {        $this->flyweights = array();    }    public function getFlyweigth($state) {        if (isset($this->flyweights[$state])) {            return $this->flyweights[$state];        } else {            return $this->flyweights[$state] = new ConcreteFlyweight($state);        }    }}$f = new FlyweightFactory();$a = $f->getFlyweigth('state A');$a->operation("other state A");$b = $f->getFlyweigth('state B');$b->operation('other state B');/* 不共享的对象，单独调用 */$u = new UnsharedConcreteFlyweight('state A');$u->operation('other state A');

运行结果

string '具体Flyweight:other state A' (length=29)string '具体Flyweight:other state B' (length=29)string '不共享的具体Flyweight:other state A' (length=41)