组合模式

【1】什么是组合模式？

将对象组合成树形结构以表示“部分整体”的层次结构。

组合模式使得用户对单个对象和组合对象的使用具有一致性。

【2】组合模式代码示例：

代码示例：
#include <iostream>
#include <vector>
#include <string>
using namespace std;

class Component
{
public:
    string name;
    Component(string name)
    {
        this->name = name;
    }
    virtual void add(Component *) = 0;
    virtual void remove(Component *) = 0;
    virtual void display(int) = 0;
};

class Leaf : public Component
{
public:
    Leaf(string name) : Component(name)
    {}
    void add(Component *c)
    {
        cout << "leaf cannot add" << endl;
    }
    void remove(Component *c)
    {
        cout << "leaf cannot remove" << endl;
    }
    void display(int depth)
    {
        string str(depth, ‘-‘);
        str += name;
        cout << str << endl;
    }
};

class Composite : public Component
{
private:
    vector<Component*> component;
public:
    Composite(string name) : Component(name)
    {}
    void add(Component *c)
    {
        component.push_back(c);
    }
    void remove(Component *c)
    {
        vector<Component*>::iterator iter = component.begin();
        while (iter != component.end())
        {
            if (*iter == c)
            {
                component.erase(iter++);
            }
            else
            {
                iter++;
            }
        }
    }
    void display(int depth)
    {
        string str(depth, ‘-‘);
        str += name;
        cout << str << endl;

        vector<Component*>::iterator iter=component.begin();
        while (iter != component.end())
        {
            (*iter)->display(depth + 2);
            iter++;
        }
    }
};


int main()
{
    Component *p = new Composite("小李"); 
    p->add(new Leaf("小王"));
    p->add(new Leaf("小强"));

    Component *sub = new Composite("小虎"); 
    sub->add(new Leaf("小王"));
    sub->add(new Leaf("小明"));
    sub->add(new Leaf("小柳"));
    
    p->add(sub);
    p->display(0);

    cout << "*******" << endl;
    sub->display(2);

    return 0;
}
//Result:
/*
小李
--小王
--小强
--小虎
----小王
----小明
----小柳
*******
--小虎
----小王
----小明
----小柳
*/