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。

  1 // Composite.cpp : 定义控制台应用程序的入口点。
  2 //
  3 
  4 #include "stdafx.h"
  5 #include<iostream>
  6 #include<string>
  7 #include <vector>
  8 #include <list>
  9 using namespace std;
 10 
 11 class Company
 12 {
 13 public:
 14     Company(string name)
 15     {
 16         m_name = name;
 17     }
 18     virtual ~Company() {}
 19     virtual void Add(Company *pCom) {}
 20     virtual void Show(int depth) {}
 21 protected:
 22     string m_name;
 23 };
 24 
 25 class ConcreteCompany : public Company 
 26 {
 27 public:
 28     ConcreteCompany(string name):Company(name) {}
 29     virtual ~ConcreteCompany() {}
 30     void Add(Company *pCom) {m_listCompany.push_back(pCom);}
 31 
 32     void Show(int depth)
 33     {
 34         for(int i = 0;i < depth; i++)
 35             cout<<"-";
 36         cout<<m_name<<endl;
 37         list<Company *>::iterator iter=m_listCompany.begin();
 38         for(; iter != m_listCompany.end(); iter++) //显示下层结点
 39             (*iter)->Show(depth + 2);
 40     }
 41 private:
 42     list<Company*> m_listCompany;
 43 
 44 };
 45 
 46 //具体的部门，财务部
 47 
 48 class FinanceDepartment : public Company 
 49 {
 50 public:
 51     FinanceDepartment(string name):Company(name){}
 52     virtual ~FinanceDepartment() {}
 53     virtual void Show(int depth) //只需显示，无限添加函数，因为已是叶结点
 54     {
 55         for(int i = 0; i < depth; i++)
 56             cout<<"-";
 57         cout<<m_name<<endl;
 58     }
 59 };
 60 
 61 class HRDepartment:public Company
 62 {
 63 public:
 64     HRDepartment(string name):Company(name){}
 65     virtual ~HRDepartment() {}
 66     virtual void Show(int depth)
 67     {
 68         for(int i = 0; i < depth; i++)
 69             cout<<"-";
 70         cout<<m_name<<endl;
 71     }
 72 };
 73 
 74 int _tmain(int argc, _TCHAR* argv[])
 75 {
 76      Company *root = new ConcreteCompany("总公司");
 77      Company *leaf1=new FinanceDepartment("财务部");
 78      Company *leaf2=new HRDepartment("人力资源部");
 79      root->Add(leaf1);
 80      root->Add(leaf2);
 81      //分公司A
 82      Company *mid1 = new ConcreteCompany("分公司A");
 83      Company *leaf3=new FinanceDepartment("财务部");
 84      Company *leaf4=new HRDepartment("人力资源部");
 85      mid1->Add(leaf3);
 86      mid1->Add(leaf4);
 87      root->Add(mid1);
 88 
 89      //分公司B
 90      Company *mid2=new ConcreteCompany("分公司B");
 91      FinanceDepartment *leaf5=new FinanceDepartment("财务部");
 92      HRDepartment *leaf6=new HRDepartment("人力资源部");
 93      mid2->Add(leaf5);
 94      mid2->Add(leaf6);
 95      root->Add(mid2);
 96      root->Show(0);
 97 
 98      delete leaf1; delete leaf2;
 99      delete leaf3; delete leaf4;
100      delete leaf5; delete leaf6;    
101      delete mid1; delete mid2;
102      delete root;
103     system("pause");
104     return 0;
105 }