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[ASP.net教程]Composite(组合)


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。