php设计模式（组合模式2）

//组合模式改进abstract class Unit{    function getComposite(){        return null;    }    abstract function bombardStrength();}abstract class CompositeUnit extends Unit{    protected $units = array();    public function getComposite(){        return $this;    }    protected function units(){        return $this->units;    }    public function removeUnit(Unit $unit){        $this->units = array_udiff($this->units,array($unit),function($a, $b){            if ($a===$b)            {                return 0;            }            return ($a>$b)?1:-1;        });    }    public function addUnit( Unit $unit){        if(in_array($unit, $this->units, true)){            return;        }        $this->units[] = $unit;    }    public function bombardStrength()    {        $ret = 0;        foreach($this->units as $unit){            $ret += $unit->bombardStrength();        }        return $ret;    }}//添加类这个类必须继承自composite；因为聚合工具类中要用到class Army extends CompositeUnit{    //public $units = [];    public function bombardStrength()    {        $ret = 0;        foreach($this->units as $unit){            $ret += $unit->bombardStrength();        }        return $ret;    }}//聚合工具类class UnitScript{    //代码解读  如果$occupyingUnit是抽象CompositeUnit的子类直接调用add    static function joinExisting(Unit $unitNew, Unit $occupyingUnit ){        $comm;        if(!is_null($comm = $occupyingUnit->getComposite())){            $comm->addUnit($unitNew);        }else{            //如果是unit的直接子类就实例化army类;            $comm = new Army();            $comm->addUnit($unitNew);            $comm->addUnit($occupyingUnit);        }        return $comm;    }}//被聚合对象class B extends Unit{    function bombardStrength(){        return 2;    }}//被聚合对象class A extends Unit{    function bombardStrength(){        return 2;    }}//如果穿进去的对象都是unit的子类，则需要实现army类，echo UnitScript::joinExisting(new B, new A)->bombardStrength();