PHP面向对象程序设计组合模式与装饰模式详解

本文实例讲述了PHP面向对象程序设计组合模式与装饰模式。分享给大家供大家参考，具体如

本文实例讲述了PHP面向对象程序设计组合模式与装饰模式。分享给大家供大家参考，具体如下：

组合模式

定义：组合模式定义了一个单根继承体系，使具有截然不同职责的集合可以并肩工作。

一个军队的案例，

<?php
abstract class Unit { // 个体
 abstract function bombardStrength();
}
class Archer extends Unit { // 弓箭手
 function bombardStrength() {
 return 4;
 }
}
class LaserCannonUnit extends Unit { // 火炮手
 function bombardStrength() {
 return 44;
 }
}
?>

军队整合成员，输出火力

<?php
abstract class Unit {
 abstract function bombardStrength();
}
class Archer extends Unit {
 function bombardStrength() {
 return 4;
 }
}
class LaserCannonUnit extends Unit {
 function bombardStrength() {
 return 44;
 }
}
class Army { // 军队
 private $units = array(); // 定义私有属性 个体集
 function addUnit( Unit $unit ) { // 添加成员
 array_push( $this->units, $unit );
 }
 function bombardStrength() { // 火力
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 return $ret;
 }
}
$unit1 = new Archer();
$unit2 = new LaserCannonUnit();
$army = new Army();
$army->addUnit( $unit1 );
$army->addUnit( $unit2 );
print $army->bombardStrength(); // 输出火力
?>

output: 48 军队进一步整合其他军队

<?php
abstract class Unit {
 abstract function bombardStrength();
}
class Archer extends Unit {
 function bombardStrength() {
 return 4;
 }
}
class LaserCannonUnit extends Unit {
 function bombardStrength() {
 return 44;
 }
}
class Army {
 private $units = array();
 private $armies= array();
 function addUnit( Unit $unit ) {
 array_push( $this->units, $unit );
 }
 function addArmy( Army $army ) {
 array_push( $this->armies, $army );
 }
 function bombardStrength() {
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 foreach( $this->armies as $army ) {
 $ret += $army->bombardStrength();
 }
 return $ret;
 }
}
$unit1 = new Archer();
$unit2 = new LaserCannonUnit();
$army = new Army();
$army->addUnit( $unit1 );
$army->addUnit( $unit2 );
print $army->bombardStrength();
print "\n";
$army2 = clone $army; // 克隆军队
$army->addArmy( $army2 );
print $army->bombardStrength();
print "\n";
?>

output: 48 96

更好的方式，支持新增，移除等等其他功能。

<?php
abstract class Unit {
 abstract function addUnit( Unit $unit );
 abstract function removeUnit( Unit $unit );
 abstract function bombardStrength();
}
class Army extends Unit { // 军队
 private $units = array();
 function addUnit( Unit $unit ) {
 if ( in_array( $unit, $this->units, true ) ) { // $this用于调用正常的属性或方法，self调用静态的方法，属性或者常量
 return;
 }
 $this->units[] = $unit;
 }
 function removeUnit( Unit $unit ) {
 // >= php 5.3
 $this->units = array_udiff( $this->units, array( $unit ),
 function( $a, $b ) { return ($a === $b)?0:1; } );
 // < php 5.3
 // $this->units = array_udiff( $this->units, array( $unit ),
 // create_function( '$a,$b', 'return ($a === $b)?0:1;' ) );
 // 对象数组，create_function,创建函数
 }
 function bombardStrength() {
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 return $ret;
 }
}
// quick example classes
class Tank extends Unit { // 坦克
 function addUnit( Unit $unit ) {}
 function removeUnit( Unit $unit ) {}
 function bombardStrength() {
 return 4;
 }
}
class Soldier extends Unit { // 士兵
 function addUnit( Unit $unit ) {}
 function removeUnit( Unit $unit ) {}
 function bombardStrength() {
 return 8;
 }
}
$tank = new Tank();
$tank2 = new Tank();
$soldier = new Soldier();
$army = new Army();
$army->addUnit( $soldier );
$army->addUnit( $tank );
$army->addUnit( $tank2 );
print_r( $army );
print $army->bombardStrength()."\n";
$army->removeUnit( $soldier );
print_r( $army );
print $army->bombardStrength()."\n";
?>

output:

Army Object
(
 [units:Army:private] => Array
 (
 [0] => Soldier Object
 (
 )
 [1] => Tank Object
 (
 )
 [2] => Tank Object
 (
 )
 )
)
16
Army Object
(
 [units:Army:private] => Array
 (
 [1] => Tank Object
 (
 )
 [2] => Tank Object
 (
 )
 )
)
8

添加异常处理

<?php
abstract class Unit {
 abstract function addUnit( Unit $unit );
 abstract function removeUnit( Unit $unit );
 abstract function bombardStrength();
}
class Army extends Unit {
 private $units = array();
 function addUnit( Unit $unit ) {
 if ( in_array( $unit, $this->units, true ) ) {
 return;
 }
 $this->units[] = $unit;
 }
 function removeUnit( Unit $unit ) {
 // >= php 5.3
 //$this->units = array_udiff( $this->units, array( $unit ),
 // function( $a, $b ) { return ($a === $b)?0:1; } );
 // < php 5.3
 $this->units = array_udiff( $this->units, array( $unit ),
 create_function( '$a,$b', 'return ($a === $b)?0:1;' ) );
 }
 function bombardStrength() {
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 return $ret;
 }
}
class UnitException extends Exception {}
class Archer extends Unit {
 function addUnit( Unit $unit ) {
 throw new UnitException( get_class($this)." is a leaf" );
 }
 function removeUnit( Unit $unit ) {
 throw new UnitException( get_class($this)." is a leaf" );
 }
 function bombardStrength() {
 return 4;
 }
}
$archer = new Archer();
$archer2 = new Archer();
$archer->addUnit( $archer2 );
?>

output:

Fatal error: Uncaught exception 'UnitException' with message 'Archer is a leaf'

点评：组合模式中的一切类都共享同一个父类型，可以轻松地在设计中添加新的组合对象或局部对象，而无需大范围地修改代码。

最终的效果，逐步优化(完美)：

<?php
class UnitException extends Exception {}
abstract class Unit {
 abstract function bombardStrength();
 function addUnit( Unit $unit ) {
 throw new UnitException( get_class($this)." is a leaf" );
 }
 function removeUnit( Unit $unit ) {
 throw new UnitException( get_class($this)." is a leaf" );
 }
}
class Archer extends Unit {
 function bombardStrength() {
 return 4;
 }
}
class LaserCannonUnit extends Unit {
 function bombardStrength() {
 return 44;
 }
}
class Army extends Unit {
 private $units = array();
 function addUnit( Unit $unit ) {
 if ( in_array( $unit, $this->units, true ) ) {
 return;
 }
 $this->units[] = $unit;
 }
 function removeUnit( Unit $unit ) {
 // >= php 5.3
 //$this->units = array_udiff( $this->units, array( $unit ),
 // function( $a, $b ) { return ($a === $b)?0:1; } );
 // < php 5.3
 $this->units = array_udiff( $this->units, array( $unit ),
 create_function( '$a,$b', 'return ($a === $b)?0:1;' ) );
 }
 function bombardStrength() {
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 return $ret;
 }
}
// create an army
$main_army = new Army();
// add some units
$main_army->addUnit( new Archer() );
$main_army->addUnit( new LaserCannonUnit() );
// create a new army
$sub_army = new Army();
// add some units
$sub_army->addUnit( new Archer() );
$sub_army->addUnit( new Archer() );
$sub_army->addUnit( new Archer() );
// add the second army to the first
$main_army->addUnit( $sub_army );
// all the calculations handled behind the scenes
print "attacking with strength: {$main_army->bombardStrength()}\n";
?>

output:

attacking with strength: 60

更牛逼的组合处理，

<?php
abstract class Unit {
 function getComposite() {
 return null;
 }
 abstract function bombardStrength();
}
abstract class CompositeUnit extends Unit { // 抽象类继承抽象类
 private $units = array();
 function getComposite() {
 return $this;
 }
 protected function units() {
 return $this->units;
 }
 function removeUnit( Unit $unit ) {
 // >= php 5.3
 //$this->units = array_udiff( $this->units, array( $unit ),
 // function( $a, $b ) { return ($a === $b)?0:1; } );
 // < php 5.3
 $this->units = array_udiff( $this->units, array( $unit ),
 create_function( '$a,$b', 'return ($a === $b)?0:1;' ) );
 }
 function addUnit( Unit $unit ) {
 if ( in_array( $unit, $this->units, true ) ) {
 return;
 }
 $this->units[] = $unit;
 }
}
class Army extends CompositeUnit {
 function bombardStrength() {
 $ret = 0;
 foreach( $this->units as $unit ) {
 $ret += $unit->bombardStrength();
 }
 return $ret;
 }
}
class Archer extends Unit {
 function bombardStrength() {
 return 4;
 }
}
class LaserCannonUnit extends Unit {
 function bombardStrength() {
 return 44;
 }
}
class UnitScript {
 static function joinExisting( Unit $newUnit,
 Unit $occupyingUnit ) { // 静态方法，直接通过类名来使用
 $comp;
 if ( ! is_null( $comp = $occupyingUnit->getComposite() ) ) { // 军队合并处理
 $comp->addUnit( $newUnit );
 } else { // 士兵合并处理
 $comp = new Army();
 $comp->addUnit( $occupyingUnit );
 $comp->addUnit( $newUnit );
 }
 return $comp;
 }
}
$army1 = new Army();
$army1->addUnit( new Archer() );
$army1->addUnit( new Archer() );
$army2 = new Army();
$army2->addUnit( new Archer() );
$army2->addUnit( new Archer() );
$army2->addUnit( new LaserCannonUnit() );
$composite = UnitScript::joinExisting( $army2, $army1 );
print_r( $composite );
?>

output:

Army Object
(
 [units:CompositeUnit:private] => Array
 (
 [0] => Archer Object
 (
 )
 [1] => Archer Object
 (
 )
 [2] => Army Object
 (
 [units:CompositeUnit:private] => Array
 (
 [0] => Archer Object
 (
 )
 [1] => Archer Object
 (
 )
 [2] => LaserCannonUnit Object
 (
 )
 )
 )
 )
)

点评：Unit 基础，CompositeUnit复合中实现add与remove。军队继承Composite，射手继承Archer。这样射手中就不会有多余的add与remove方法了。

装饰模式

装饰模式帮助我们改变具体组件的功能。

看例子

<?php
abstract class Tile { // 砖瓦
 abstract function getWealthFactor(); // 获取财富
}
class Plains extends Tile { // 平原
 private $wealthfactor = 2;
 function getWealthFactor() {
 return $this->wealthfactor;
 }
}
class DiamondPlains extends Plains { // 钻石地段
 function getWealthFactor() {
 return parent::getWealthFactor() + 2;
 }
}
class PollutedPlains extends Plains { // 污染地段
 function getWealthFactor() {
 return parent::getWealthFactor() - 4;
 }
}
$tile = new PollutedPlains();
print $tile->getWealthFactor();
?>

output: -2

点评：不具有灵活性，我们不能同时获得钻石与被污染的土地的资金情况。

装饰模式使用组合和委托而不是只使用继承来解决功能变化的问题。

看例子：

<?php
abstract class Tile {
 abstract function getWealthFactor();
}
class Plains extends Tile {
 private $wealthfactor = 2;
 function getWealthFactor() {
 return $this->wealthfactor;
 }
}
abstract class TileDecorator extends Tile { // 装饰
 protected $tile;
 function __construct( Tile $tile ) {
 $this->tile = $tile;
 }
}
class DiamondDecorator extends TileDecorator { // 钻石装饰
 function getWealthFactor() {
 return $this->tile->getWealthFactor()+2;
 }
}
class PollutionDecorator extends TileDecorator { // 污染装饰
 function getWealthFactor() {
 return $this->tile->getWealthFactor()-4;
 }
}
$tile = new Plains();
print $tile->getWealthFactor(); // 2
$tile = new DiamondDecorator( new Plains() );
print $tile->getWealthFactor(); // 4
$tile = new PollutionDecorator(
 new DiamondDecorator( new Plains() ));
print $tile->getWealthFactor(); // 0
?>

output: 2 4 0

点评：这个模型具有扩展性。我们不需要创建DiamondPollutionPlains对象就可以构建一个钻石被污染的对象。

一个更逼真的例子

<?php
class RequestHelper{} // 请求助手
abstract class ProcessRequest { // 进程请求
 abstract function process( RequestHelper $req );
}
class MainProcess extends ProcessRequest { // 主进程
 function process( RequestHelper $req ) {
 print __CLASS__.": doing something useful with request\n";
 }
}
abstract class DecorateProcess extends ProcessRequest { // 装饰进程
 protected $processrequest;
 function __construct( ProcessRequest $pr ) { // 引用对象，委托
 $this->processrequest = $pr;
 }
}
class LogRequest extends DecorateProcess { // 日志请求
 function process( RequestHelper $req ) {
 print __CLASS__.": logging request\n"; // 当前类,有点递归的感觉
 $this->processrequest->process( $req );
 }
}
class AuthenticateRequest extends DecorateProcess { // 认证请求
 function process( RequestHelper $req ) {
 print __CLASS__.": authenticating request\n";
 $this->processrequest->process( $req );
 }
}
class StructureRequest extends DecorateProcess { // 组织结构请求
 function process( RequestHelper $req ) {
 print __CLASS__.": structuring request\n";
 $this->processrequest->process( $req );
 }
}
$process = new AuthenticateRequest( new StructureRequest(
 new LogRequest (
 new MainProcess()
 ))); // 这样可以很灵活的组合进程的关系，省去很多重复的继承
$process->process( new RequestHelper() );
print_r($process);
?>

output:

AuthenticateRequest: authenticating request
StructureRequest: structuring request
LogRequest: logging request
MainProcess: doing something useful with request
AuthenticateRequest Object
(
 [processrequest:protected] => StructureRequest Object
 (
 [processrequest:protected] => LogRequest Object
 (
 [processrequest:protected] => MainProcess Object
 (
 )
 )
 )
)

点评：这里有一种递归的感觉，一层调用一层。模式是牛人总结出来用于灵活的解决一些现实问题的。牛！给开发多一点思路。