设计模式C++描述----11.组合(Composite)模式
上一篇：http://www.2cto.com/kf/201205/132469.html
一. 举例
这个例子是书上的，假设有一个公司的组结结构如下：
它的结构很像一棵树，其中人力资源部和财务部是没有子结点的，具体公司才有子结点。
而且最关健的是，它的每一层结构很相似。
代码实现如下：
[cpp] view plaincopyprint?//公司类，提供接口
class Company
{
public:
Company(string name)
{
m_name = name;
}
virtual ~Company()
{}
virtual void Add(Company *pCom)
{}
virtual void Display(int depth)
{}
protected:
string m_name;
};
//具体公司
class ConcreteCompany : public Company
{
public:
ConcreteCompany(string name): Company(name)
{}
virtual ~ConcreteCompany()
{}
//增加子树或叶子
void Add(Company *pCom)
{
m_listCompany.push_back(pCom);
}
//显示
void Display(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)->Display(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()
{}
//只需显示，无限添加函数，因为已是叶结点
virtual void Display(int depth)
{
for(int i = 0; i < depth; i++)
cout<<"-";
cout<< m_name << endl;
}
};
//具体的部门，人力资源部
class HRDepartment :public Company
{
public:
HRDepartment(string name):Company(name)
{}
virtual ~HRDepartment()
{}
//只需显示，无限添加函数，因为已是叶结点
virtual void Display(int depth)
{
for(int i = 0; i < depth; i++)
{
cout<<"-";
}
cout<< m_name << endl;
}
};
//////////////////////////////////////////////////////////////////////////
//测试代码
int main()
{
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);
//华东分公司
Company *mid1 = new ConcreteCompany("华东分公司");
Company *leaf3=new FinanceDepartment("华东分公司财务部");
Company *leaf4=new HRDepartment("华东分公司人力资源部");
mid1->Add(leaf3);
mid1->Add(leaf4);
root->Add(mid1);
//南京办事处
Company *mid2=new ConcreteCompany("南京办事处");
FinanceDepartment *leaf5=new FinanceDepartment("南京办事处财务部");
HRDepartment *leaf6=new HRDepartment("南京办事处人力资源部");
mid2->Add(leaf5);
mid2->Add(leaf6);
root->Add(mid2);
//杭州办事处
Company *mid3=new ConcreteCompany("杭州办事处");
FinanceDepartment *leaf7=new FinanceDepartment("杭州办事处财务部");
HRDepartment *leaf8=new HRDepartment("杭州办事处人力资源部");
mid3->Add(leaf7);
mid3->Add(leaf8);
mid2->Add(mid3);
root->Display(0);
delete leaf1;
delete leaf2;
delete leaf3;
delete leaf4;
delete leaf5;
delete leaf6;
delete leaf7;
delete leaf8;
delete mid1;
delete mid2;
delete root;
return 0;
}
//公司类，提供接口
class Company
{
public:
Company(string name)
{
m_name = name;
}
virtual ~Company()
{}
virtual void Add(Company *pCom)
{}
virtual void Display(int depth)
{}
protected:
string m_name;
};
//具体公司 www.2cto.com
class ConcreteCompany : public Company
{
public:
ConcreteCompany(string name): Company(name)
{}
virtual ~ConcreteCompany()
{}
//增加子树或叶子
void Add(Company *pCom)
{
m_listCompany.push_back(pCom);
}
//显示
void Display(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)->Display(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()
{}
//只需显示，无限添加函数，因为已是叶结点
virtual void Display(int depth)
{
for(int i = 0; i < depth; i++)
cout<<"-";
cout<< m_name << endl;
}
};
//具体的部门，人力资源部
class HRDepartment :public Company
{
public:
HRDepartment(string name):Company(name)
{}
virtual ~HRDepartment()
{}
//只需显示，无限添加函数，因为已是叶结点
virtual void Display(int depth)
{
for(int i = 0; i < depth; i++)
{
cout<<"-";
}
cout<< m_name << endl;
}
};
//////////////////////////////////////////////////////////////////////////
//测试代码
int main()
{
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);
//华东分公司
Company *mid1 = new ConcreteCompany("华东分公司");
Company *leaf3=new FinanceDepartment("华东分公司财务部");
Company *leaf4=new HRDepartment("华东分公司人力资源部");
mid1->Add(leaf3);
mid1->Add(leaf4);
root->Add(mid1);
//南京办事处
Company *mid2=new ConcreteCompany("南京办事处");
FinanceDepartment *leaf5=new FinanceDepartment("南京办事处财务部");
HRDepartment *leaf6=new HRDepartment("南京办事处人力资源部");
mid2->Add(leaf5);
mid2->Add(leaf6);
root->Add(mid2);
//杭州办事处
Company *mid3=new ConcreteCompany("杭州办事处");
FinanceDepartment *leaf7=new FinanceDepartment("杭州办事处财务部");
HRDepartment *leaf8=new HRDepartment("杭州办事处人力资源部");
mid3->Add(leaf7);
mid3->Add(leaf8);
mid2->Add(mid3);
root->Display(0);
delete leaf1;
delete leaf2;
delete leaf3;
delete leaf4;
delete leaf5;
delete leaf6;
delete leaf7;
delete leaf8;
delete mid1;
delete mid2;
delete root;
return 0;
}
二. 说明
1. 上面公司的结构图其实就是整体与部分的关系，而且的话整体与部分可以一致对待，因为有很多相似之处嘛。
2. 这棵树有两种几能，要么是棵叶，要么是子棵。
其实这种模式就是组合模式。
三. 组合模式
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。
要注意两点：
1. “树形”，必须是一种层次结构，有可以向下延伸的分枝，也有不变的树叶。
2. "一致性"，也就是要具有很多相似性。
结构图如下：
component：主要是定义统一的接口，说白了也就是提取出相似性。
composite：定义分枝节点，也就是子树。
leaf：定义叶节点，叶节点是没有子节点的。
作者 lwbeyond
