《大话设计模式》学习笔记15：组合模式

　　

　　

公司管理系统示例：

　　

1.Component：

    public abstract class Company
    {
        protected string name;
        public Company(string name)
        {
            this.name = name;
        }
        public abstract void Add(Company company);
        public abstract void Remove(Company company);
        public abstract void Display(int depth);
        public abstract void LineOfDuty();
    }

2.Composite：

    public class ConcreteCompany:Company
    {
        private IList<Company> companys = new List<Company>();
        public ConcreteCompany(string name)
            :base(name)
        {

        }
        public override void Add(Company company)
        {
            companys.Add(company);
        }

        public override void Remove(Company company)
        {
            companys.Remove(company);
        }

        public override void Display(int depth)
        {
            Console.WriteLine(new string('-',depth) + name);
            foreach(var company in companys)
            {
                company.Display(depth + 2);
            }
        }

        public override void LineOfDuty()
        {
            foreach(var company in companys)
            {
                company.LineOfDuty();
            }
        }
    }

3.Leaf：

    public class HRDepartment:Company
    {
        public HRDepartment(string name)
            :base(name)
        {

        }
        public override void Add(Company company)
        {
            
        }

        public override void Remove(Company company)
        {
            
        }

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

        public override void LineOfDuty()
        {
            Console.WriteLine("{0} 员工招聘培训管理",name);
        }
    }

    public class FinanceDepartment:Company
    {
        public FinanceDepartment(string name)
            : base(name)
        {

        }
        public override void Add(Company company)
        {
            
        }

        public override void Remove(Company company)
        {
            
        }

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

        public override void LineOfDuty()
        {
            Console.WriteLine("{0} 公司财务收支管理",name);
        }
    }

4.客户端代码：

    class Program
    {
        static void Main(string[] args)
        {
            Company rootCompany = new ConcreteCompany("北京总公司");
            rootCompany.Add(new HRDepartment("总公司人力资源部"));
            rootCompany.Add(new FinanceDepartment("总公司财务部"));

            Company eastCompany = new ConcreteCompany("华东分公司");
            eastCompany.Add(new HRDepartment("华东分公司人力资源部"));
            eastCompany.Add(new FinanceDepartment("华东分公司财务部"));

            rootCompany.Add(eastCompany);

            Company shanghaiCompany = new ConcreteCompany("上海办事处");
            shanghaiCompany.Add(new HRDepartment("上海办事处人力资源部"));
            shanghaiCompany.Add(new FinanceDepartment("上海办事处财务部"));

            eastCompany.Add(shanghaiCompany);

            Console.WriteLine("机构图：");
            rootCompany.Display(1);

            Console.WriteLine("职责：");
            rootCompany.LineOfDuty();
        }
    }

　　透明方式：Component中声明所有用来管理子对象的方法，其中包括Add、Move等。这样实现Componet接口的所有子类都具备了Add和Remove。这样做的好处就是叶节点和枝节点对于外界没有区别，它们具备完全一致的行为接口。但问题也很明显，因为Leaf类本身不具备Add()、Remove()方法的功能，所以实现它是完全没有意义的。

　　安全方式：Componet中不去声明Add和Remove方法，那么子类Leaf也就不需要去实现它，而是在Composite声明所有用来管理子类对象的方法。不过由于不够透明，所以树叶和树枝类将不具有相同的接口，客户端的调用要做相应的判断，带来了不便。