组合模式

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。

代码背景为：餐厅里面的菜单，菜单里有菜单构成了树形结构。

#include <iostream>
#include <string>
#include <list>
using namespace std;

class MenuComponent
{
public:
	virtual void add(MenuComponent* menuComponent) {	}
	virtual void remove(MenuComponent* menuComponent) {	}
	virtual MenuComponent* getChild(int i) 
	{
		MenuComponent* menuComponent;
		return menuComponent;
	}
	virtual string getName() { return "hi";}
	virtual string getDescription() {return "hi";}
	virtual double getPrice() {return 0.0;	}
	virtual bool isVegetarian() {return true; }
	virtual void print() {	}
};
class Menu : public MenuComponent
{
public:
	list<MenuComponent*>* menuComponents;
	string name;
	string description;
	Menu(string name, string description)
	{
		menuComponents = new list<MenuComponent*>();
		this->name = name;
		this->description = description;
	}
	virtual void add(MenuComponent* menuComponent)
	{
		menuComponents->push_back(menuComponent);
	}
	virtual void remove(MenuComponent* menuComponent)
	{
		menuComponents->remove(menuComponent);
	}
	virtual MenuComponent* getChild(int i)
	{
		list<MenuComponent*>::iterator iter = menuComponents->begin();
		while(i-- && iter != menuComponents->end())
			iter++;
		if(iter != menuComponents->end())
			return (MenuComponent*)(*iter);
	}
	virtual string getName()
	{
		return name;
	}
	virtual string getDescription()
	{
		return description;
	}
	virtual void print()
	{
		cout<<endl<<getName()<<", " << getDescription()<<endl << "-------------"<<endl;
		list<MenuComponent*>::iterator iter = menuComponents->begin();
		while(iter != menuComponents->end())
		{
			(*iter)->print();
			++iter;
		}
	}
};
class MenuItem : public MenuComponent 
{  
public:  
	string name;  
	string description;  
	bool vegetarian;  
	double price;  
	MenuItem(){ }  

	MenuItem(string name,   
		string description,   
		bool vegetarian,  
		double price)  
	{  
		this->name = name;  
		this->description = description;  
		this->vegetarian = vegetarian;  
		this->price = price;  
	}  

	virtual string getName()  
	{  
		return name;  
	}  
	virtual string getDescription()  
	{  
		return description;  
	}  
	virtual double getPrice()  
	{  
		return price;  
	}  
	virtual bool isVegetarian()  
	{  
		return vegetarian;  
	}  
	virtual void print()
	{
		cout<<" "<<getName();
		if(isVegetarian())
			cout<<"(v)";
		cout <<", " <<getPrice()<<endl;
		cout <<"   ---" << getDescription()<<endl;
	}
};
class Waitress
{
public:
	MenuComponent* allMennus;
	Waitress(MenuComponent* allMennus)
	{
		this->allMennus = allMennus;
	}
	void printMenu()
	{
		allMennus->print();
	}
};

int main()
{
	MenuComponent* pancakeHouseMenu = 
		new Menu("PANCAKE HOUSE MENU", "Breakfast");
	MenuComponent* dinerMenu = 
		new Menu("DINER MENU", "Lunch");
	MenuComponent* cafeMenu = 
		new Menu("CAFE MENU", "Dinner");
	MenuComponent* dessertMenu = 
		new Menu("DESSERT MENU", "Dessert of course!");
	MenuComponent* coffeeMenu = new Menu("COFFEE MENU", "Stuff to go with your afternoon coffee");

	MenuComponent* allMenus = new Menu("ALL MENUS", "All menus combined");

	allMenus->add(pancakeHouseMenu);
	allMenus->add(dinerMenu);
	allMenus->add(cafeMenu);

	pancakeHouseMenu->add(new MenuItem(
		"K&B's Pancake Breakfast", 
		"Pancakes with scrambled eggs, and toast", 
		true,
		2.99));
	pancakeHouseMenu->add(new MenuItem(
		"Regular Pancake Breakfast", 
		"Pancakes with fried eggs, sausage", 
		false,
		2.99));
	pancakeHouseMenu->add(new MenuItem(
		"Blueberry Pancakes",
		"Pancakes made with fresh blueberries, and blueberry syrup",
		true,
		3.49));
	pancakeHouseMenu->add(new MenuItem(
		"Waffles",
		"Waffles, with your choice of blueberries or strawberries",
		true,
		3.59));

	dinerMenu->add(new MenuItem(
		"Vegetarian BLT",
		"(Fakin') Bacon with lettuce & tomato on whole wheat", 
		true, 
		2.99));
	dinerMenu->add(new MenuItem(
		"BLT",
		"Bacon with lettuce & tomato on whole wheat", 
		false, 
		2.99));
	dinerMenu->add(new MenuItem(
		"Soup of the day",
		"A bowl of the soup of the day, with a side of potato salad", 
		false, 
		3.29));
	dinerMenu->add(new MenuItem(
		"Hotdog",
		"A hot dog, with saurkraut, relish, onions, topped with cheese",
		false, 
		3.05));
	dinerMenu->add(new MenuItem(
		"Steamed Veggies and Brown Rice",
		"Steamed vegetables over brown rice", 
		true, 
		3.99));

	dinerMenu->add(new MenuItem(
		"Pasta",
		"Spaghetti with Marinara Sauce, and a slice of sourdough bread",
		true, 
		3.89));

	dinerMenu->add(dessertMenu);

	dessertMenu->add(new MenuItem(
		"Apple Pie",
		"Apple pie with a flakey crust, topped with vanilla icecream",
		true,
		1.59));

	dessertMenu->add(new MenuItem(
		"Cheesecake",
		"Creamy New York cheesecake, with a chocolate graham crust",
		true,
		1.99));
	dessertMenu->add(new MenuItem(
		"Sorbet",
		"A scoop of raspberry and a scoop of lime",
		true,
		1.89));

	cafeMenu->add(new MenuItem(
		"Veggie Burger and Air Fries",
		"Veggie burger on a whole wheat bun, lettuce, tomato, and fries",
		true, 
		3.99));
	cafeMenu->add(new MenuItem(
		"Soup of the day",
		"A cup of the soup of the day, with a side salad",
		false, 
		3.69));
	cafeMenu->add(new MenuItem(
		"Burrito",
		"A large burrito, with whole pinto beans, salsa, guacamole",
		true, 
		4.29));

	cafeMenu->add(coffeeMenu);

	coffeeMenu->add(new MenuItem(
		"Coffee Cake",
		"Crumbly cake topped with cinnamon and walnuts",
		true,
		1.59));
	coffeeMenu->add(new MenuItem(
		"Bagel",
		"Flavors include sesame, poppyseed, cinnamon raisin, pumpkin",
		false,
		0.69));
	coffeeMenu->add(new MenuItem(
		"Biscotti",
		"Three almond or hazelnut biscotti cookies",
		true,
		0.89));

	Waitress* waitress = new Waitress(allMenus);

	waitress->printMenu();
	return 0;
}