设计模式：组合模式

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组合模式：将对象组合成树形结构以表示“部分-真题”的结构层次。组合模式使得用户对单个对象和组合对象的使用具有一致性。

结构图：

using System;using System.Collections.Generic;using System.Text;namespace 组合模式{    class Program    {        static void Main(string[] args)        {            Composite root = new Composite("root");            root.Add(new Leaf("Leaf A"));            root.Add(new Leaf("Leaf B"));            Composite comp = new Composite("Composite X");            comp.Add(new Leaf("Leaf XA"));            comp.Add(new Leaf("Leaf XB"));            root.Add(comp);            Composite comp2 = new Composite("Composite XY");            comp2.Add(new Leaf("Leaf XYA"));            comp2.Add(new Leaf("Leaf XYB"));            comp.Add(comp2);            root.Add(new Leaf("Leaf C"));            Leaf leaf = new Leaf("Leaf D");            root.Add(leaf);            root.Remove(leaf);            root.Display(1);            Console.Read();        }    }     abstract class Component    {        protected string name;        public Component(string name)        {            this.name = name;        }        public abstract void Add(Component c);        public abstract void Remove(Component c);        public abstract void Display(int depth);    }    class Composite : Component    {        private List<Component> children = new List<Component>();        public Composite(string name)            : base(name)        { }        public override void Add(Component c)        {            children.Add(c);        }        public override void Remove(Component c)        {            children.Remove(c);        }        public override void Display(int depth)        {            Console.WriteLine(new String('-', depth) + name);            foreach (Component component in children)            {                component.Display(depth + 2);            }        }    }    class Leaf : Component    {        public Leaf(string name)            : base(name)        { }        public override void Add(Component c)        {            Console.WriteLine("Cannot add to a leaf");        }        public override void Remove(Component c)        {            Console.WriteLine("Cannot remove from a leaf");        }        public override void Display(int depth)        {            Console.WriteLine(new String('-', depth) + name);        }    }}

Composite

当你发现需求中是体现部分与整体的结构时，以及你希望用户可以忽略组合对象与单个对象的不同，统一地使用组合结构中的多有对象时，就应该考虑用组合模式。

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