模式定义：

组合模式允许你将对象组合成树形结构来表现“整体/部分”层次结构。组合能让客户以一致的方式处理个别对象以及对象组合。

这个模式能够创建一个树形结构，在同一个结构中处理嵌套菜单和菜单项组。通过菜单和项放在相同结构中，我们创建了一个“整体/部分”层次结构，即由菜单和菜单项组成的对象树。使用组合结构，我们能把相同的操作应用在组合和个别对象上。换句话说，在大多数情况下，我们可以忽略对象组合和个别对象之间的差别。

模式结构：

Component:

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编程实现及执行结果：

#include 
  
   
#include 
   
     #include 
    
      #include 
     
       using namespace std; //菜单和菜单项共同的
      组件 class MenuComponent { public: virtual void add(MenuComponent* menuComponent) { throw exception("add error!"); } virtual void remove(MenuComponent* menuComponent) { throw exception("remove error!"); } virtual MenuComponent* getChild(int i) { throw exception("getChild error"); } virtual string getName() { throw exception("getName error"); } virtual string getDescription() { throw exception("getDescription error"); } virtual double getPrice() { throw exception("getPrice error"); } virtual void print() { throw exception("print error"); } }; //菜单项类 class MenuItem : public MenuComponent { public: MenuItem(){} MenuItem(string na, string descrip, double pric) { name = na; description = descrip; price = pric; } string getName() { return name; } string getDescription() { return description; } double getPrice() { return price; } void print() { cout << " " << getName() << ", " << getPrice() <<" ---" << getDescription() << endl; } private: string name; string description; double price; }; //组合菜单类 class Menu : public MenuComponent { public: Menu(string nam, string descri) { name = nam; description = descri; } void add(MenuComponent* pMenuComponent) { pMenuComponents.push_back(pMenuComponent); } void remove(MenuComponent* pMenuComponent) { vector
      
       ::iterator iter = pMenuComponents.begin(); for(; iter!=pMenuComponents.end(); ++iter) { if(*iter == pMenuComponent) { pMenuComponents.erase(iter); } } } MenuComponent* getChild(int i) { return pMenuComponents[i]; } string getName() { return name; } string getDescription() { return description; } void print() { cout << endl << getName() << ", " << getDescription() << endl << "--------------" << endl; vector
       
        ::iterator iter = pMenuComponents.begin(); while(iter != pMenuComponents.end()) { MenuComponent* pMenuComponent = *iter; pMenuComponent->print(); ++iter; } } private: vector
        
          pMenuComponents; string name; string description; }; //服务生类 class Waitress { public: Waitress(MenuComponent* all_Menus) { allMenus = all_Menus; } void printMenu() { allMenus->print(); } private: MenuComponent* allMenus; }; //客户代码 int main() { MenuComponent* pancakeHouseMenu = new Menu("PANCAKE HOUSE MENU", "Breakfast"); MenuComponent* dinerMenu = new Menu("Diner MENU", "Lunch"); MenuComponent* dessertMenu = new Menu("DESSERT MENU","Dessert of coure!"); MenuComponent* allMenus = new Menu("ALL Menus", "All menus combined"); allMenus->add(pancakeHouseMenu); allMenus->add(dinerMenu); dinerMenu->add(new MenuItem("Pasta","Spaheti with Sauce", 3.89)); dinerMenu->add(dessertMenu); dessertMenu->add(new MenuItem("Apple Pie", "App pie with a cruse", 1.59)); Waitress* waitress = new Waitress(allMenus); waitress->printMenu(); return 0; } 
        
       
      
     
    
   
  

执行结果：

ALLMenus, All menus combined

--------------

PANCAKEHOUSE MENU, Breakfast

--------------

DinerMENU, Lunch

--------------

Pasta, 3.89 ---Spaheti with Sauce

DESSERTMENU, Dessert of coure!

--------------

Apple Pie, 1.59 ---App pie with a cruse

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