php 设计模式（组合模式一）

//组合模式
abstract class Unit{
    abstract function addUnit(Unit $unit);
    abstract function removeUnit(Unit $unit);
    abstract function bombardStrength();
}
class Army extends Unit{
    public $unit = [];
    public function addUnit(Unit $unit){

        if(in_array($unit, $this->unit,true)){
            return;
        }
        $this->unit[] = $unit;
    }
    public function removeUnit(Unit $unit){
        $this->unit = array_udiff($this->unit, [$unit], function($a,$b){
            if ($a===$b)
            {
                return 0;
            }
            return ($a>$b)?1:-1;
        });
    }
    public function bombardStrength()
    {
        $ret = 0;
        foreach($this->unit as $unit){
            $ret += $unit->bombardStrength();
        }
        return $ret;
    }
}
//缺点所有子类都必须实现抽象的add和remove方法，我们仅仅需要组合类拥有add和remove方法
class Archer extends Unit{
    public function addUnit(Unit $unit)
    {
        // TODO: Implement addUnit() method.
    }
    public function removeUnit(Unit $unit)
    {
        // TODO: Implement removeUnit() method.
    }
    public function bombardStrength()
    {
        return 4;
    }
}
class   Brcher extends Unit{
    public function addUnit(Unit $unit)
    {
        // TODO: Implement addUnit() method.
    }
    public function removeUnit(Unit $unit)
    {
        // TODO: Implement removeUnit() method.
    }
    public function bombardStrength()
    {
        return 2;
    }
}

$ar = new Army();
$a = new Archer();
$b = new Brcher();
$ar->addUnit($a);
$ar->addUnit($b);
print_r($ar->unit);
$ar->removeUnit($b);
print_r($ar->unit);
echo $ar->bombardStrength();