B1:模板方法模式 TemplateMethod

abstract class Product
{
    protected $payPrice = 0;
 
    public final function setAdjustment()
    {
        $this->payPrice += $this->discount();
        $this->payPrice += $this->tax();
    }
 
    public function getPayPrice()
    {
        return $this->payPrice;
    }
 
    protected function discount()
    {
        return 0;
    }
 
    abstract protected function tax();
}
 
class CD extends Product
{
    public function __construct($price)
    {
        $this->payPrice = $price;
    }
 
    protected function tax()
    {
        return 0;
    }
}
 
class IPhone extends Product
{
    public function __construct($price)
    {
        $this->payPrice = $price;
    }
 
    protected function tax()
    {
        return $this->payPrice * 0.2;
    }
 
    protected function discount()
    {
        return -10;
    }
 
}
 
$cd = new CD(15);
$cd->setAdjustment();
echo $cd->getPayPrice();
 
$iphone = new IPhone(6000);
$iphone->setAdjustment();
echo $iphone->getPayPrice();