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)：