php - What is the proper way to call methods from a decorator where the method doesn't modify the functionality?

Question

From this example, is CoffeeWithCream's getBrand() method improper or problematic in any way? My reason for doing it this way is to avoid writing $coffeeWithCream->$coffee->getBrand() everywhere it's called.

Particularly, one area of concern that's surfaced is unit testing. I'm not comfortable enough yet with Unit Testing to know whether this strategy complicates testing.

Also, I know that getBrand() is just a simple accessor method. What if the method performed a more complex task, would the answer change?

Class Coffee {
    public $brand;
    public $ingredients = array('coffee');

    public function getBrand() {
        return $this->brand;
    }

    public function getIngredients() {
        return $this->ingredients;
    }
}

Class CoffeeWithCream {
    public $coffee;

    public __construct(Coffee $coffee) {
        $this->coffee = $coffee;
    }

    public function getIngredients() {
        $ingredients = $this->coffee->getIngredients();
        $ingredients[] = 'cream';
        return $ingredients;
    }

    public function getBrand() {
        $this->coffee->getBrand();
    }
}

Answer 1

您应该实现一个抽象装饰器类，它使用与咖啡类相同的接口。这个抽象类主要用于将所有方法调用传递给 Coffee 类。您的具体装饰器从抽象装饰器扩展而来，并且只覆盖他们想要添加功能的特定方法。请参考Wiki 这样你就可以摆脱 $coffeeWithCream->$coffee->getBrand() 的问题了。

interface ICoffee 
{
    public function getBrand();

    public function getIngredients();
}


class Coffee implements ICoffee { ... }


abstract class CoffeeDecorator implements ICoffee
{

    protected $coffee;      

    public function __construct(Coffee $coffee)
    {
        $this->coffee = $coffee;
    }

    public function getBrand()
    {
        return $this->coffee->getBrand();
    }

    public function getIngredients()
    {
        return $this->coffee->getIngredients();
    }  

}


class CoffeeWithCream extends CoffeeDecorator
{

    public function getIngredients() 
    {
        $ingredients = parent::getIngredients();
        $ingredients[] = 'cream';
        return $ingredients;
    }

}