PHP中组合模式与装饰模式的示例分析

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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，

军队整合成员，输出火力

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

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。

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

添加异常处理

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)：

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( $sub_army );// all the calculations handled behind the scenesprint "attacking with strength: {$main_army->bombardStrength()}\n";?>

output:

attacking with strength: 60

更牛逼的组合处理，

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

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：

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

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 requestStructureRequest: structuring requestLogRequest: logging requestMainProcess: doing something useful with requestAuthenticateRequest Object(  [processrequest:protected] => StructureRequest Object    (      [processrequest:protected] => LogRequest Object        (          [processrequest:protected] => MainProcess Object            (            )        )    ))

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