[DP] 裝飾者模式

寫個簡易範例來幫助了解裝飾者模式

Drink Class 相關

namespace Beverage
{
    public abstract class Drink
    {
        protected string DrinkName = string.Empty;
        protected decimal DrinkPrice = 0.0m;

        public virtual string GetDrinkName()
        {
            return DrinkName;
        }
        
        public abstract string GetDescript();
        public abstract decimal GetPrice();
    }

    public class GreeTea : Drink
    {
        public GreeTea()
        {
            this.DrinkName = "綠茶";
            this.DrinkPrice = 15m;
        }

        public override string GetDrinkName()
        {
            return DrinkName;
        }

        public override string GetDescript()
        {
            return $"{DrinkName} ( {DrinkPrice} )";
        }

        public override decimal GetPrice()
        {
            return DrinkPrice;
        }
    }
}

Decorator Class 相關

namespace Beverage
{
    public abstract class Decorator : Drink
    {
        protected Drink drink;
        protected string DecoratorName = string.Empty;
        protected decimal DecoratorPrice = 0.0m;

        public Decorator(Drink drink)
        {
            this.drink = drink;
        }

        public override string GetDrinkName()
        {
            return drink.GetDrinkName();
        }

        public override string GetDescript()
        {
            return drink.GetDescript() + $", {DecoratorName} ( {DecoratorPrice} )";
        }

        public override decimal GetPrice()
        {
            return drink.GetPrice() + DecoratorPrice;
        }
    }

    public class Bubble : Decorator
    {
        public Bubble(Drink drink) : base(drink)
        {
            this.DecoratorName = "珍珠";
            this.DecoratorPrice = 10m;
        }
    }

    public class Milk : Decorator
    {
        public Milk(Drink drink) : base(drink)
        {
            this.DecoratorName = "牛奶";
            this.DecoratorPrice = 21m;
        }
    }

    public class Yakult : Decorator
    {
        public Yakult(Drink drink) : base(drink)
        {
            this.DecoratorName = "養樂多";
            this.DecoratorPrice = 10m;
        }

        public override string GetDrinkName()
        {
            return $"{DecoratorName} - {drink.GetDrinkName()}";
        }
    }
}

執行

namespace Beverage
{
    class Program
    {
        static void Main(string[] args)
        {
            Drink d1 = new GreeTea();
            d1 = new Bubble(d1);
            d1 = new Yakult(d1);
            ShowData(d1);
        }

        private static void ShowData(Drink d)
        {
            Console.WriteLine($"品名：{d.GetDrinkName()}");
            Console.WriteLine($"價格：{d.GetPrice()}");
            Console.WriteLine($"說明：{d.GetDescript()}");
        }

    }
}

結果

參考資料
• 大話設計模式
• 裝飾者模式筆記
• [Design Pattern] 裝飾者模式 (Decorate Pattern) 義大利麵餐館