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(); 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 + );
}
}
} 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。