结构型设计模式之组合模式(Composite)

结构
意图	将对象组合成树形结构以表示“部分-整体”的层次结构。C o m p o s i t e 使得用户对单个对象和组合对象的使用具有一致性。
适用性	你想表示对象的部分-整体层次结构。 你希望用户忽略组合对象与单个对象的不同，用户将统一地使用组合结构中的所有对象。

  using System;
     using System.Collections;

     abstract class Component
     {
         protected string strName;

         public Component(string name)
         {
             strName = name;
         }

         abstract public void Add(Component c);

         public abstract void DumpContents();

         // other operations for delete, get, etc.
     }

     class Composite : Component
     {
         private ArrayList ComponentList = new ArrayList();

         public Composite(string s) : base(s) {}

         override public void Add(Component c)
         {
             ComponentList.Add(c);
         }

         public override void DumpContents()
         {
             // First dump the name of this composite node
             Console.WriteLine("Node: {0}", strName);

             // Then loop through children, and get then to dump their contents
             foreach (Component c in ComponentList)
             {
                 c.DumpContents();
             }
         }
     }

     class Leaf : Component
     {
         public Leaf(string s) : base(s) {}

         override public void Add(Component c)
         {
             Console.WriteLine("Cannot add to a leaf");
         }

         public override void DumpContents()
         {
             Console.WriteLine("Node: {0}", strName);
         }
     }

     /// <summary>
     ///    Summary description for Client.
     /// </summary>
     public class Client
     {
         Component SetupTree()
         {
             // here we have to create a tree structure,
             // consisting of composites and leafs.
             Composite root = new Composite("root-composite");
             Composite parentcomposite;
             Composite composite;
             Leaf leaf;

             parentcomposite = root;
             composite = new Composite("first level - first sibling - composite");
             parentcomposite.Add(composite);
             leaf = new Leaf("first level - second sibling - leaf");
             parentcomposite.Add(leaf);
             parentcomposite = composite;
             composite = new Composite("second level - first sibling - composite");
             parentcomposite.Add(composite);
             composite = new Composite("second level - second sibling - composite");
             parentcomposite.Add(composite);

             // we will leaf the second level - first sibling empty, and start
             // populating the second level - second sibling
             parentcomposite = composite;
             leaf = new Leaf("third level - first sibling - leaf");
             parentcomposite.Add(leaf);

             leaf = new Leaf("third level - second sibling - leaf");
             parentcomposite.Add(leaf);
             composite = new Composite("third level - third sibling - composite");
             parentcomposite.Add(composite);

             return root;
         }

         public static int Main(string[] args)
         {
                Component component;
             Client c = new Client();
             component = c.SetupTree();

             component.DumpContents();
             return ;
         }
     }

组合模式