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 = 0;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 + 2);
    }
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 = 0; 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 = 0; 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(0);

     delete leaf1; delete leaf2;
     delete leaf3; delete leaf4;
     delete leaf5; delete leaf6;    
     delete mid1; delete mid2;
     delete root;
    system("pause");
    return 0;
}