Decorator pattern - a good example

decorator_pattern_example.txt

interface IProduct {
    getName();
    getPrice();
}

class Product implements IProduct {
    private $name;
    private $price;

    getName() {...}
    getPrice() {...}
}

/**
 * A product that is added to customer's basket for free (a gift).
 */
class GiftProduct implements IProduct {
    private $product;

    __construct(IProduct $product) {
        $this->product = $product;
    }
    
    getName() {
        return $this->product->getName() . " (gift)";
    }
    
    getPrice() {
        return 0;       //gifts are for free
    }
}

/**
 * More than one product sold as one set (bundle), eg. a laptop + mouse.
 */
class SetOfProducts implements IProduct {
    private $name;
    private $products = [];
    
    __construct($name) {
        $this->name = $name;
    }
    
    addComponent(IProduct $product) {
        $this->products[] = $product;
    }
    
    getName() {
        return $this->name;
    }
    
    getPrice() {
        //return sum of prices of all the products
    }
}