设计模式之装饰器-AOP

HelloWorld简单例子如下：此例子好好体会下继承 is a和组合 has a的异同。

using System;
using System.Runtime.InteropServices;

namespace TestEnviroment
{
    class Program
    {
        static void Main(string[] args)
        {
            BaseClass ins = new Ins();
            ins = new Before(ins);
            ins = new After(ins);
            ins.Do();
            Console.ReadLine();
        }
    }
    public abstract class BaseClass
    {
        public abstract void Do();
    }
    public class Ins : BaseClass
    {
        public override void Do()
        {
            Console.Write("World");     //底层行为
        }
    }
    public abstract class BaseDecorator: BaseClass
    {
        public BaseClass baseClass;
        public BaseDecorator(BaseClass baseClass)
        {
            this.baseClass = baseClass;
        }
    }
    public class After : BaseDecorator
    {
        public After(BaseClass baseClass) : base(baseClass) { }
        public override void Do()
        {
            base.baseClass.Do();
            Console.Write(" Jack");     //扩展区
        }
    }
    public class Before: BaseDecorator
    {
        public Before(BaseClass baseClass) : base(baseClass) { }
        public override void Do()
        {
            Console.Write("Hello ");     //扩展区
            base.baseClass.Do();
        }
    }
}

下面是综合例子：

using System;
using System.Drawing;
using System.Runtime.InteropServices;

namespace TestEnviroment
{
    public interface IText
    {
        string Content { get; }
    }
    /// <summary>
    /// 状态接口
    /// </summary>
    public interface IState
    {
        bool Equals(IState newState);
    }
    public interface IDecorator : IText
    {
        IState State { get; set; }
        void Refresh<T>(IState newState) where T : IDecorator;
    }

    public abstract class DecoratorBase : IDecorator
    {
        protected IText target;
        public DecoratorBase(IText target)
        {
            this.target = target;
        }
        public abstract string Content { get; }
        protected IState state;
        public IState State { get => this.state; set => this.state = value; }

        public virtual void Refresh<T>(IState newState) where T : IDecorator
        {
            if (this.GetType() == typeof(T))
            {
                if (newState == null) state = null;
                if (State != null && !State.Equals(newState))
                {
                    State = newState;
                }
                return;
            }
            if (target != null)
            {
                ((IDecorator)target).Refresh<T>(newState);
            }
        }
    }

    public class BoldState : IState
    {
        public bool IsBold;
        public bool Equals(IState newState)
        {
            if (newState == null) return false;
            return ((BoldState)newState).IsBold == IsBold;
        }
    }

    public class ColorState : IState
    {
        public Color Color = Color.Black;
        public bool Equals(IState newState)
        {
            if (newState == null) return false;
            return ((ColorState)newState).Color == Color;
        }
    }

    /// <summary>
    /// 具体装饰类
    /// </summary>
    public class BoldDecorator : DecoratorBase
    {
        public BoldDecorator(IText target) : base(target)
        {
            base.state = new BoldState();
        }

        public override string Content
        {
            get
            {
                if (((BoldState)State).IsBold)
                    return $"<b>{target.Content}</b>";
                else
                    return target.Content;
            }
        }
    }

    /// <summary>
    /// 具体装饰类
    /// </summary>
    public class ColorDecorator : DecoratorBase
    {
        public ColorDecorator(IText target) : base(target)
        {
            base.state = new ColorState();
        }
        public override string Content
        {
            get
            {
                string colorName = ((ColorState)State).Color.Name;
                return $"<{colorName}>{target.Content}</{colorName}>";
            }
        }
    }
    /// <summary>
    /// 具体装饰类
    /// </summary>
    public class BlockAllDecorator : DecoratorBase
    {
        public BlockAllDecorator(IText target) : base(target) { }
        public override string Content => string.Empty;
    }
    public class TextObject : IText
    {
        public string Content => "hello";
    }

    class Program
    {
        static void Main(string[] args)
        {
            IText text = new TextObject();
            text = new BoldDecorator(text);
            text = new ColorDecorator(text);

            ColorState newColorState = new ColorState();
            newColorState.Color = Color.Red;
            IDecorator root = (IDecorator)text;
            root.Refresh<ColorDecorator>(newColorState);
            Console.WriteLine($"color text.Content={text.Content}");
            BoldState newBoldState = new BoldState();
            newBoldState.IsBold = true;
            root.Refresh<BoldDecorator>(newBoldState);
            Console.WriteLine($"bold text.Content={text.Content}");

            text = new BlockAllDecorator(text);
            Console.WriteLine($"text.Content={text.Content}");
            Console.ReadLine();
        }
    }
}