装饰器模式

类图

2024072116162888.png

最核心的点在于，装饰器也要实现 Component 接口。这样，当新增类时，就不需要修改客户端代码，满足开闭原则

代码

<?php
 
// 组件接口
interface Coffee
{
    public function getPrice(): int;
}
 
class lightRoastCoffee implements Coffee
{
    public function getPrice(): int
    {
        return 10;
    }
}
 
class darkRoastCoffee implements Coffee
{
    public function getPrice(): int
    {
        return 15;
    }
}
 
// 装饰器
 
abstract class CoffeeDecorator implements Coffee
{
    protected $coffee;
 
    public function __construct(Coffee $coffee)
    {
        $this->coffee = $coffee;
    }
 
    public function getPrice(): int
    {
        return $this->coffee->getPrice();
    }
}
 
class MilkDecorator extends CoffeeDecorator
{
    public function getPrice(): int
    {
        return $this->coffee->getPrice() + 5;
    }
}
 
class SugarDecorator extends CoffeeDecorator
{
    public function getPrice(): int
    {
        return $this->coffee->getPrice() + 2;
    }
}
 
// client
function getPrice(Coffee $coffee)
{
    return $coffee->getPrice();
}
 
$lighRoastCoffee = new lightRoastCoffee();
$dakRoastCoffee = new darkRoastCoffee();
 
$milkDecorator = new MilkDecorator($lighRoastCoffee);
 
echo getPrice($milkDecorator);
 
$sugarDecorator = new SugarDecorator($dakRoastCoffee);
 
echo getPrice($sugarDecorator);