Composite（组合）--对象结构型模式

1.意图

将对象组合成树形结构以表示“部分-整体”的层次结构。Composite使得用户对单个对象和组合对象的使用具有一致性。

2.动机

可以组合多个简单组件以形成一些较大的组件，这些组件又可以组合成更大的组件。Composite模式描述了如何使用递归组合，使得用户不必对这些类进行区别。

3.适用性

表示对象的部分-整体层次结构。
希望用户忽略组合对象与单个对象的不同，用户将统一地使用组合结构中的所有对象。

4.结构

5.代码实例

#include <memory>
#include <vector>

class Graphic
{
public:
    Graphic(std::shared_ptr<Graphic> pParent);
    virtual void Add(std::shared_ptr<Graphic>& pGraphic);
    virtual void Remove(std::shared_ptr<Graphic>& pGraphic);
    virtual std::shared_ptr<Graphic> GetChild(int iIndex);
    virtual std::shared_ptr<Graphic>& GetParent();
    virtual void Opereate();

protected:
    std::shared_ptr<Graphic> m_pParent;

    std::vector<std::shared_ptr<Graphic>> m_vecChildrenGraphics;

}; 

class Circle : public Graphic
{
public:
    Circle(std::shared_ptr<Graphic> pParent);
    void Opereate();
};


class Retangle : public Graphic
{
public:
    Retangle(std::shared_ptr<Graphic> pParent);
    void Opereate();
};


class Line : public Graphic
{
public:
    Line(std::shared_ptr<Graphic> pParent);
    void Opereate();
};

class Picture : public Graphic
{
public:
    Picture(std::shared_ptr<Graphic> pParent);
    virtual void Add(std::shared_ptr<Graphic>& pGraphic);
    virtual void Remove(std::shared_ptr<Graphic>& pGraphic);
    virtual std::shared_ptr<Graphic> GetChild(int iIndex);
    void Opereate();
};

#include "Graphic.h"
#include <iostream>


Graphic::Graphic(std::shared_ptr<Graphic> pParent) 
    : m_pParent(pParent)
{
}

 void Graphic::Add(std::shared_ptr<Graphic>& pGraphic)
 {
     std::cout<< "Leaf Cannot Add Childrren" << std::endl;
 }

 void Graphic::Remove(std::shared_ptr<Graphic>& pGraphic)
 {
     std::cout<< "Leaf Cannot Remove Childrren" << std::endl;
 }

 std::shared_ptr<Graphic> Graphic::GetChild(int iIndex)
 {
     std::cout<< "Leaf Cannot Get Child" << std::endl;
     return nullptr;
 }

 std::shared_ptr<Graphic>& Graphic::GetParent()
 {
     return m_pParent;
 }

 void Graphic::Opereate()
 {
     std::cout<< "Default Operate Executed" <<std::endl;
 }

 Circle::Circle(std::shared_ptr<Graphic> pParent)
     :Graphic(pParent)
 {
 }

 void Circle::Opereate()
 {
     std::cout << "Circle Operate Exeeuted" << std::endl;
 }

 Retangle::Retangle(std::shared_ptr<Graphic> pParent)
     :Graphic(pParent)
 {
 }

 void Retangle::Opereate()
 {
     std::cout << "Retangle Operate Exeeuted" << std::endl;
 }


  Line::Line(std::shared_ptr<Graphic> pParent)
     :Graphic(pParent)
 {
 }

 void Line::Opereate()
 {
     std::cout << "Line Operate Exeeuted" << std::endl;
 }


 Picture::Picture(std::shared_ptr<Graphic> pParent) 
    : Graphic(pParent)
{
}

 void Picture::Add(std::shared_ptr<Graphic>& pGraphic)
 {
     m_vecChildrenGraphics.push_back(pGraphic);

     std::cout<< "ChildrenGraphics Add Success" <<std::endl;
 }

 void Picture::Remove(std::shared_ptr<Graphic>& pGraphic)
 {
     for(auto iter=m_vecChildrenGraphics.begin();
         iter!=m_vecChildrenGraphics.end();++iter)
     {
         if((*iter) == pGraphic)
         {
             m_vecChildrenGraphics.erase(iter);
             std::cout<< "ChildrenGraphics remove Success"<<std::endl;
             break;
         }
     }
 }

 std::shared_ptr<Graphic> Picture::GetChild(int iIndex)
 {
     auto count = m_vecChildrenGraphics.size();
     if(iIndex <= count -1)
     {
         std::cout<< "Get Child Success" <<std::endl;
         return m_vecChildrenGraphics[iIndex];
     }

     return nullptr;
 }

 void Picture::Opereate()
 {
     for(auto iter=m_vecChildrenGraphics.begin();
         iter!=m_vecChildrenGraphics.end();++iter)
     {
         (*iter)->Opereate();
     }
 }

#include "Graphic.h"
#include <iostream>

int main()
{
    std::shared_ptr<Graphic> pPicture(new Picture(nullptr));

    std::shared_ptr<Graphic> pCircle(new Circle(pPicture));

    std::shared_ptr<Graphic> pRetangle(new Retangle(pPicture));

    std::shared_ptr<Graphic> pLine(new Line(pPicture));

    pPicture->Add(pCircle);
    pPicture->Add(pRetangle);
    pPicture->Add(pLine);

    pPicture->Opereate();

    if(nullptr == pPicture->GetParent())
    {
        std::cout<< "pPicture is root" <<std::endl;
    }

    auto pNode = pPicture->GetChild(0);

    auto pParent = pNode->GetParent();

    if(nullptr != pParent)
    {
        std::cout<<"Node has Parent"<<std::endl;
    }

    std::cout << "Parent Operate:"<<std::endl;

    pParent->Opereate();

    pNode->Opereate();

    pNode->Add(pNode);

    pNode->Remove(pNode);

    pNode->GetChild(0);


    pNode = pPicture->GetChild(1);

    if(nullptr != pNode->GetParent())
    {
        std::cout<<"Node has Parent"<<std::endl;
    }

    pNode->Opereate();

    pNode->Add(pNode);

    pNode->Remove(pNode);

    pNode->GetChild(0);

     pNode = pPicture->GetChild(2);

    if(nullptr != pNode->GetParent())
    {
        std::cout<<"Node has Parent"<<std::endl;
    }

    pNode->Opereate();

    pNode->Add(pNode);

    pNode->Remove(pNode);

    pNode->GetChild(0);

    pPicture->Remove(pCircle);
    pPicture->Remove(pRetangle);
    pPicture->Remove(pLine);


    while(1);

    



}

6.测试结果

7.效果

定义了包含基本对象和组合对象的类层次结构基本对象可以被组合成更复杂的组合对象，而这个组合对象又可以被组合。
简化客户代码客户可以一致地使用组合结构和单个对象。
使得容易增加新类型的组件新定义的Composite或Leaf子类自动地与已有的结构和客户代码一起工作，客户程序不需因新的Component类而改变。
使设计变的更加一般化。