组合模式

Composite，将对象组合成树形结构以表示”部分——整体“的层次结构。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。

就是套娃，一层套一层。

    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 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);
        }
    }

    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);
            //通过循环遍历将所有的子节点都输出
            foreach (Component component in children)
            {
                component.Display(depth + 2);
            }
        }
    }

调用样例：

        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"));

            //这里就将 Composite 分配到root下了，套了第一层
            root.Add(comp);

            Composite comp2 = new Composite("Composite XY");
            comp2.Add(new Leaf("Leaf XYA"));
            comp2.Add(new Leaf("Leaf XYB"));

            //这里套了第二层
            comp.Add(comp2);
            root.Display(2);

            comp.Remove(comp2);
            root.Display(2);

            Console.ReadLine();
        }