设计模式（14）---组合模式

一、定义

组合模式：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。

解释：简单来说，编写一个类，该类能作用于整体，并且编写整体中的部分时也能使用该类，而不用做大的更改。

二、UML类图及基本代码

设计模式（14）---组合模式

基本代码：

abstract class Component
    {
        protected string name;

        public Component(string name)
        {
            this.name = name;
        }

        public abstract void Add(Component component);
        public abstract void Remove(Component component);
        public abstract void Display(int depth);
    }

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

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

        public override void Remove(Component component)
        {
            Console.WriteLine("cannot remove to a leaf");
        }

        public override void Display(int depth)
        {
            Console.WriteLine(new string('-', depth) + name);
        }
    }

    class Composite : Component
    {
        private IList<Component> children = new List<Component>();

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

        public override void Add(Component component)
        {
            children.Add(component);
        }

        public override void Remove(Component component)
        {
            children.Remove(component);
        }

        public override void Display(int depth)
        {
            Console.WriteLine(new string('-', depth) + name);

            foreach (Component component in children)
            {
                component.Display(depth + 2);
            }
        }
    }

客户端进行调用：

Composite root = new Composite("root");
            root.Add(new Leaf("leaf A"));
            root.Add(new Leaf("leaf B"));

            Composite composite = new Composite("Composite X");
            composite.Add(new Leaf("leaf XA"));
            composite.Add(new Leaf("leaf XB"));
            root.Add(composite);

            Composite composite2 = new Composite("Composite XY");
            composite2.Add(new Leaf("leaf XYA"));
            composite2.Add(new Leaf("leaf XYB"));
            composite.Add(composite2);

            root.Add(new Leaf("leaf C"));

            Leaf leaf = new Leaf("Leaf D");
            root.Add(leaf);
            root.Remove(leaf);

            root.Display(1);

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