用最简单的例子理解复合模式(Composite Pattern)

在显示树形结构时，复合模式有很好的体现。本篇显示如下部门结构：

以上，有的节点包含子节点，有的节点部包含子节点。不管是什么节点，每个节点就代表一个部门。

 

首先设计一个关于部门的抽象基类。

    public abstract class DepartmentComponent
    {
        public string Name { private set; get; }
        public DepartmentComponent(string name)
        {
            this.Name = name;
        }
        public virtual void PrintSupervisorOf(int spacing)
        {
            for (int counter = 0; counter < spacing; counter++)
            {
                Console.Write(" ");
            }
            Console.WriteLine(Name);
        }
    }

以上，通过构造函数给属性赋值，通过PrintSupervisorOf(int spacing)方法打印出节点的名称。

 

接下来设计包含子节点的节点。该类维护着DepartmentComponent类型的集合，提供方法向这个集合中添加节点或从集合中删除节点。

    public class DepartmentComposite : DepartmentComponent
    {
        private IList<DepartmentComponent> employees;
        public DepartmentComposite(string name) : base(name)
        {
            employees = new List<DepartmentComponent>();
        }
        public void AddDepartment(DepartmentComponent e)
        {
            employees.Add(e);
        }
        public void RemoveDepartment(DepartmentComponent e)
        {
            employees.Remove(e);
        }
        public override void PrintSupervisorOf(int spacing)
        {
            base.PrintSupervisorOf(spacing);
            foreach (DepartmentComponent e in employees)
            {
                e.PrintSupervisorOf(spacing + 1);
            }
        }
    }

以上 PrintSupervisorOf(int spacing)方法重写了抽象基类的方法，不仅把本节点的名称打印出来，还使用递归把所有子节点的名称显示出来。

 

最后设计部包含子节点的节点。

    public class Department : DepartmentComponent
    {
        public Department(string name) : base(name)
        {
            
        }
        public override void PrintSupervisorOf(int spacing)
        {
            base.PrintSupervisorOf(spacing);
        }
    }

客户端部分。

    class Program
    {
        static void Main(string[] args)
        {
            DepartmentComposite salesDepartment1 = new DepartmentComposite("销售部1");
            Department zhangsan = new Department("张三");
            Department lisi = new Department("李四");
            DepartmentComposite salesDepartment2 = new DepartmentComposite("销售部2");
            DepartmentComposite specialDepartment = new DepartmentComposite("销售部2特别行动组");
            Department wangwu = new Department("王五");
            Department zhaoliu = new Department("赵六");
            DepartmentComposite salesDepartment = new DepartmentComposite("销售部");
            salesDepartment.AddDepartment(salesDepartment1);
            salesDepartment.AddDepartment(salesDepartment2);
            salesDepartment1.AddDepartment(zhangsan);
            salesDepartment1.AddDepartment(lisi);
            salesDepartment2.AddDepartment(specialDepartment);
            specialDepartment.AddDepartment(wangwu);
            specialDepartment.AddDepartment(zhaoliu);
            salesDepartment.PrintSupervisorOf(0);
            Console.ReadKey();
        }
    }