《PHP實(shí)戰(zhàn)：學(xué)習(xí)php設(shè)計(jì)模式 php實(shí)現(xiàn)享元模式(flyweight)》要點(diǎn)：
本文介紹了PHP實(shí)戰(zhàn)：學(xué)習(xí)php設(shè)計(jì)模式 php實(shí)現(xiàn)享元模式(flyweight)，希望對(duì)您有用。如果有疑問(wèn)，可以聯(lián)系我們。
PHP教程一、意圖
運(yùn)用共享技術(shù)有效的支持大量細(xì)粒度的對(duì)象
享元模式變化的是對(duì)象的存儲(chǔ)開(kāi)銷
二、享元模式結(jié)構(gòu)圖
PHP教程
PHP教程三、享元模式中主要角色
抽象享元(Flyweight)角色：此角色是所有的具體享元類的超類,為這些類規(guī)定出需要實(shí)現(xiàn)的公共接口.那些需要外蘊(yùn)狀態(tài)的操作可以通過(guò)調(diào)用商業(yè)以參數(shù)形式傳入
具體享元(ConcreteFlyweight)角色：實(shí)現(xiàn)Flyweight接口,并為內(nèi)部狀態(tài)(如果有的話)拉回存儲(chǔ)空間.ConcreteFlyweight對(duì)象必須是可共享的.它所存儲(chǔ)的狀態(tài)必須是內(nèi)部的
不共享的具體享元(UnsharedConcreteFlyweight)角色：并非所有的Flyweight子類都需要被共享.Flyweigth使共享成為可能,但它并不強(qiáng)制共享.
享元工廠(FlyweightFactory)角色：負(fù)責(zé)創(chuàng)建和管理享元角色.本角色必須保證享元對(duì)象可能被系統(tǒng)適當(dāng)?shù)毓蚕?br>客戶端(Client)角色：本角色需要維護(hù)一個(gè)對(duì)所有享元對(duì)象的引用.本角色需要自行存儲(chǔ)所有享元對(duì)象的外部狀態(tài)
四、享元模式的優(yōu)點(diǎn)和缺點(diǎn)
享元模式的優(yōu)點(diǎn)：Flyweight模式可以大幅度地降低內(nèi)存中對(duì)象的數(shù)量.
享元模式的缺點(diǎn)：
1、Flyweight模式使得系統(tǒng)更加復(fù)雜
2、Flyweigth模式將享元對(duì)象的狀態(tài)外部化,而讀取外部狀態(tài)使得運(yùn)行時(shí)間稍微變長(zhǎng)
五、享元模式適用場(chǎng)景
當(dāng)以下情況都成立時(shí)使用Flyweight模式：
1、一個(gè)應(yīng)用程序使用了大量的對(duì)象
2、完全由于使用大量的對(duì)象,造成很大的存儲(chǔ)開(kāi)銷
3、對(duì)象的大多數(shù)狀態(tài)都可變?yōu)橥獠繝顟B(tài)
4、如果刪除對(duì)象的外部狀態(tài),那么可以用相對(duì)較少的共享對(duì)象取代很多組對(duì)象
5、應(yīng)用程序不依賴于對(duì)象標(biāo)識(shí).
六、享元模式與其它模式
單例模式(Singleton)：客戶端要引用享元對(duì)象,是通過(guò)工廠對(duì)象創(chuàng)建或者獲得的,客戶端每次引用一個(gè)享元對(duì)象,都是可以通過(guò)同一個(gè)工廠對(duì)象來(lái)引用所需要的享元對(duì)象.因此,可以將享元工廠設(shè)計(jì)成單例模式,這樣就可以保證客戶端只引用一個(gè)工廠實(shí)例.因?yàn)樗械南碓獙?duì)象都是由一個(gè)工廠對(duì)象統(tǒng)一管理的,所以在客戶端沒(méi)有必要引用多個(gè)工廠對(duì)象.不管是單純享元模式還是復(fù)合享元模式中的享元工廠角色,都可以設(shè)計(jì)成為單例模式,對(duì)于結(jié)果是不會(huì)有任何影響的.
Composite模式：復(fù)合享元模式實(shí)際上是單純享元模式與合成模式的組合.單純享元對(duì)象可以作為樹(shù)葉對(duì)象來(lái)講,是可以共享的,而復(fù)合享元對(duì)象可以作為樹(shù)枝對(duì)象,因此在復(fù)合享元角色中可以添加聚集管理辦法.
七、享元模式PHP示例
PHP教程
<?php
/**
* 抽象享元角色
*/
abstract class Flyweight {
/**
* 示意性辦法
* @param string $state 外部狀態(tài)
*/
abstract public function operation($state);
}
/**
* 具體享元角色
*/
class ConcreteFlyweight extends Flyweight {
private $_intrinsicState = null;
/**
* 構(gòu)造辦法
* @param string $state 內(nèi)部狀態(tài)
*/
public function __construct($state) {
$this->_intrinsicState = $state;
}
public function operation($state) {
echo 'ConcreteFlyweight operation, Intrinsic State = ' . $this->_intrinsicState
. ' Extrinsic State = ' . $state . '<br />';
}
}
/**
* 不共享的具體享元,客戶端直接調(diào)用
*/
class UnsharedConcreteFlyweight extends Flyweight {
private $_intrinsicState = null;
/**
* 構(gòu)造辦法
* @param string $state 內(nèi)部狀態(tài)
*/
public function __construct($state) {
$this->_intrinsicState = $state;
}
public function operation($state) {
echo 'UnsharedConcreteFlyweight operation, Intrinsic State = ' . $this->_intrinsicState
. ' Extrinsic State = ' . $state . '<br />';
}
}
/**
* 享元工廠角色
*/
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);
}
}
}
/**
* 客戶端
*/
class Client {
/**
* Main program.
*/
public static function main() {
$flyweightFactory = new FlyweightFactory();
$flyweight = $flyweightFactory->getFlyweigth('state A');
$flyweight->operation('other state A');
$flyweight = $flyweightFactory->getFlyweigth('state B');
$flyweight->operation('other state B');
/* 不共享的對(duì)象,單獨(dú)調(diào)用 */
$uflyweight = new UnsharedConcreteFlyweight('state A');
$uflyweight->operation('other state A');
}
}
Client::main();
?>
PHP教程八、復(fù)合享元模式
復(fù)合享元模式對(duì)象是由一些單純享元使用合成模式加以復(fù)合而成
復(fù)合享元角色所代表的對(duì)象是不可以共享的,但是一個(gè)復(fù)合享元對(duì)象可以分解成為多個(gè)本身是單純享元對(duì)象的組合.
九、復(fù)合享元模式PHP示例
PHP教程
<?php
/**
* 抽象享元角色
*/
abstract class Flyweight {
/**
* 示意性辦法
* @param string $state 外部狀態(tài)
*/
abstract public function operation($state);
}
/**
* 具體享元角色
*/
class ConcreteFlyweight extends Flyweight {
private $_intrinsicState = null;
/**
* 構(gòu)造辦法
* @param string $state 內(nèi)部狀態(tài)
*/
public function __construct($state) {
$this->_intrinsicState = $state;
}
public function operation($state) {
echo 'ConcreteFlyweight operation, Intrinsic State = ' . $this->_intrinsicState
. ' Extrinsic State = ' . $state . '<br />';
}
}
/**
* 不共享的具體享元,客戶端直接調(diào)用
*/
class UnsharedConcreteFlyweight extends Flyweight {
private $_flyweights;
/**
* 構(gòu)造辦法
* @param string $state 內(nèi)部狀態(tài)
*/
public function __construct() {
$this->_flyweights = array();
}
public function operation($state) {
foreach ($this->_flyweights as $flyweight) {
$flyweight->operation($state);
}
}
public function add($state, Flyweight $flyweight) {
$this->_flyweights[$state] = $flyweight;
}
}
/**
* 享元工廠角色
*/
class FlyweightFactory {
private $_flyweights;
public function __construct() {
$this->_flyweights = array();
}
public function getFlyweigth($state) {
if (is_array($state)) { // 復(fù)合模式
$uFlyweight = new UnsharedConcreteFlyweight();
foreach ($state as $row) {
$uFlyweight->add($row, $this->getFlyweigth($row));
}
return $uFlyweight;
} else if (is_string($state)) {
if (isset($this->_flyweights[$state])) {
return $this->_flyweights[$state];
} else {
return $this->_flyweights[$state] = new ConcreteFlyweight($state);
}
} else {
return null;
}
}
}
/**
* 客戶端
*/
class Client {
/**
* Main program.
*/
public static function main() {
$flyweightFactory = new FlyweightFactory();
$flyweight = $flyweightFactory->getFlyweigth('state A');
$flyweight->operation('other state A');
$flyweight = $flyweightFactory->getFlyweigth('state B');
$flyweight->operation('other state B');
/* 復(fù)合對(duì)象*/
$uflyweight = $flyweightFactory->getFlyweigth(array('state A', 'state B'));
$uflyweight->operation('other state A');
}
}
Client::main();
?>
PHP教程十、PHP中享元模式的地位
相對(duì)于其它模式,Flyweight模式在PHP的現(xiàn)有版本中沒(méi)有太大的意義,因?yàn)镻HP的生命周期是頁(yè)面級(jí)的,即從一個(gè)PHP文件執(zhí)行開(kāi)始會(huì)載入所需的資源,當(dāng)執(zhí)行完畢后,這些所有的資源會(huì)被全部釋放,而一般來(lái)說(shuō)我們也不會(huì)讓一個(gè)頁(yè)面執(zhí)行太長(zhǎng)時(shí)間.
PHP教程以上就是使用php實(shí)現(xiàn)享元模式的代碼,還有一些關(guān)于享元模式的概念區(qū)分,希望對(duì)大家的學(xué)習(xí)有所贊助.
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