{C#}设计模式辨析.装饰器

背景

• 不修改旧类的前提下，通过嵌套类增加功能

示例

using static System.Console;

namespace DesignPattern_Decorator
{
    // 抽象类：保证子类互换性+共用方法
    public abstract class Character
    {
        public abstract void Show();
    }

    // 实体类，被装饰对象
    public class Hero : Character
    {
        public override void Show()
            => WriteLine("I am Mario.");
    }

    // 装饰处理类，可在实体类上增加功能
    // 抽象类，保证装饰后结果的互换性+禁止新建实例
    public abstract class Decorator : Character
    {
        private readonly Character hero;

        public Decorator(Character hero)
        {
            this.hero = hero;
        }

        public override void Show() => hero.Show();
    }

    // 装饰结果类
    public class Driver : Decorator
    {
        public Driver(Character hero) : base(hero) { }

        public override void Show()
        {
            base.Show();
            WriteLine("I am also a driver.");
        }
    }

    // 装饰结果类
    public class Teacher : Decorator
    {
        public Teacher(Character hero) : base(hero) { }

        public override void Show()
        {
            base.Show();
            WriteLine("I am also a teacher.");
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var hero = new Hero();
            var driver = new Driver(hero);
            var teacher = new Teacher(driver);
            teacher.Show();
            ReadKey();
        }
    }
}