C++设计模式之组合模式

DP书上给出的定义：将对象组合成树形结构以表示“部分-整体”的层次结构。组合使得用户对单个对象和组合对象的使用具有一致性。注意两个字“树形”。这种树形结构在现实生活中随处可见，比如一个集团公司，它有一个母公司，下设很多家子公司。不管是母公司还是子公司，都有各自直属的财务部、人力资源部、销售部等。对于母公司来说，不论是子公司，还是直属的财务部、人力资源部，都是它的部门。整个公司的部门拓扑图就是一个树形结构。

下面给出组合模式的UML图。从图中可以看到，FinanceDepartment、HRDepartment两个类作为叶结点，因此没有定义添加函数。而ConcreteCompany类可以作为中间结点，所以可以有添加函数。那么怎么添加呢？这个类中定义了一个链表，用来放添加的元素。

 // Composite.cpp : 定义控制台应用程序的入口点。
 //

 #include "stdafx.h"
 #include<iostream>
 #include<string>
 #include <vector>
 #include <list>
 using namespace std;

 class Company
 {
 public:
     Company(string name)
     {
         m_name = name;
     }
     virtual ~Company() {}
     virtual void Add(Company *pCom) {}
     virtual void Show(int depth) {}
 protected:
     string m_name;
 };

 class ConcreteCompany : public Company
 {
 public:
     ConcreteCompany(string name):Company(name) {}
     virtual ~ConcreteCompany() {}
     void Add(Company *pCom) {m_listCompany.push_back(pCom);}

     void Show(int depth)
     {
         for(int i = ;i < depth; i++)
             cout<<"-";
         cout<<m_name<<endl;
         list<Company *>::iterator iter=m_listCompany.begin();
         for(; iter != m_listCompany.end(); iter++) //显示下层结点
             (*iter)->Show(depth + );
     }
 private:
     list<Company*> m_listCompany;

 };

 //具体的部门，财务部

 class FinanceDepartment : public Company
 {
 public:
     FinanceDepartment(string name):Company(name){}
     virtual ~FinanceDepartment() {}
     virtual void Show(int depth) //只需显示，无限添加函数，因为已是叶结点
     {
         for(int i = ; i < depth; i++)
             cout<<"-";
         cout<<m_name<<endl;
     }
 };

 class HRDepartment:public Company
 {
 public:
     HRDepartment(string name):Company(name){}
     virtual ~HRDepartment() {}
     virtual void Show(int depth)
     {
         for(int i = ; i < depth; i++)
             cout<<"-";
         cout<<m_name<<endl;
     }
 };

 int _tmain(int argc, _TCHAR* argv[])
 {
      Company *root = new ConcreteCompany("总公司");
      Company *leaf1=new FinanceDepartment("财务部");
      Company *leaf2=new HRDepartment("人力资源部");
      root->Add(leaf1);
      root->Add(leaf2);
      //分公司A
      Company *mid1 = new ConcreteCompany("分公司A");
      Company *leaf3=new FinanceDepartment("财务部");
      Company *leaf4=new HRDepartment("人力资源部");
      mid1->Add(leaf3);
      mid1->Add(leaf4);
      root->Add(mid1);

      //分公司B
      Company *mid2=new ConcreteCompany("分公司B");
      FinanceDepartment *leaf5=new FinanceDepartment("财务部");
      HRDepartment *leaf6=new HRDepartment("人力资源部");
      mid2->Add(leaf5);
      mid2->Add(leaf6);
      root->Add(mid2);
      root->Show();

      delete leaf1; delete leaf2;
      delete leaf3; delete leaf4;
      delete leaf5; delete leaf6;
      delete mid1; delete mid2;
      delete root;
     system("pause");
     return ;
 }