《headfirst设计模式》读书笔记9-迭代器和组合模式

目录

1、封装遍历2、定义迭代器模式

2.1 部分源码

2.1.1 MenuItem.h2.1.2 Menu.h2.1.3 Iterator.h2.1.4 ArrayIterator.h2.1.5 ArrayIterator.cpp2.1.6 DinerMenu.h2.1.7 DinerMenu.cpp 3、单一责任4、定义组合模式

4.1 类图和部分源码

4.1.1 MenuComponent.h4.1.2 MenuItem.h4.1.3 Menu.h4.1.4 Waitress.h4.1.5 main.cpp 5、组合迭代器 1、封装遍历

因为早餐和午餐的遍历方式不同，这样在遍历菜单时由于不同的遍历方式不方便。
当我们对遍历进行封装就会对实现遍历的统一

2、定义迭代器模式

通过类图我们可以知道：
Iterator是一个接口，通过实现接口内的方法达到遍历的标准
Aggregate是聚合的接口，通过对迭代器接口的引用实现对迭代器的解耦
Client通过对两边接口的引用实现了集合和迭代器的解耦

2.1 部分源码 2.1.1 MenuItem.h

#include using std::string;class MenuItem{public: string name; string description; bool vegetarian; double price; MenuItem(); MenuItem(string name,string description,bool vegetarian,double price); string getName(); string getDescription(); double getPrice(); bool isVegetarian(); string toString();};

2.1.2 Menu.h

#include "Iterator.h"class Menu{public: virtual Iterator *createIterator()=0; virtual ~Menu(){};};

2.1.3 Iterator.h

#include "MenuItem.h"class Iterator{public: virtual bool hasNext()=0; virtual MenuItem *next()=0; virtual ~Iterator(){};};

2.1.4 ArrayIterator.h

#include "Iterator.h"#include "MenuItem.h"class ArrayIterator:public Iterator{public: ArrayIterator(MenuItem items[],int size); virtual MenuItem *next()override final; virtual bool hasNext()override final; virtual ~ArrayIterator();private: MenuItem *items; int position=0; int size=0;};

2.1.5 ArrayIterator.cpp

#include "ArrayIterator.h"ArrayIterator::ArrayIterator(MenuItem items[], int size){ this->items=items; this->size=size;}MenuItem *ArrayIterator::next(){ return &items[position++];}bool ArrayIterator::hasNext(){ if(position>=size)return false; else return true;}ArrayIterator::~ArrayIterator(){}

2.1.6 DinerMenu.h

#include "Menu.h"#include "MenuItem.h"#include "Iterator.h"#include "ArrayIterator.h"class DinerMenu:public Menu{public: DinerMenu(); void addItem(string name,string description,bool vegetarian, double price); MenuItem *getMenuItems(); virtual Iterator *createIterator()override final; virtual ~DinerMenu();private: int numberOfItems=0; MenuItem *menuItems;};

2.1.7 DinerMenu.cpp

#include "DinerMenu.h"#include "iostream"int MAX_ITEMS = 6;DinerMenu::DinerMenu(){ menuItems=new MenuItem[MAX_ITEMS]; menuItems[0]=MenuItem("Vegetarian BLT", "(Fakin') Bacon with lettuce & tomato on whole wheat", true, 2.99); menuItems[1]=MenuItem("BLT", "Bacon with lettuce & tomato on whole wheat", false, 2.99); menuItems[2]=MenuItem("Soup of the day", "Soup of the day, with a side of potato salad", false, 3.29); menuItems[3]=MenuItem("Hotdog", "A hot dog, with sauerkraut, relish, onions, topped with cheese", false, 3.05); menuItems[4]=MenuItem("Steamed Veggies and Brown Rice", "Steamed vegetables over brown rice", true, 3.99); menuItems[5]=MenuItem("Pasta", "Spaghetti with Marinara Sauce, and a slice of sourdough bread", true, 3.89); numberOfItems=6;}void DinerMenu::addItem(std::string name, std::string description, bool vegetarian, double price){ MenuItem menuItem=MenuItem(name,description,vegetarian,price); if(numberOfItems>=MAX_ITEMS){ std::cout<<"Sorry, menu is full! Can't add item to menu"<

3、单一责任

如果允许一个类既要管理集合又要提供遍历，当集合改变需要改变类，当遍历改变也要改变类，所以尽量使一个类只有一个责任

4、定义组合模式

在前面我们都是一个菜单一个菜单独立出来的，但是当我们菜单中又要嵌套菜单这咋办？

组合模式就是定义一个超类，两个具体类继承，一个类可以嵌套超类就相当于菜单（这样就可以嵌套菜单也可以嵌套菜单项），另一个就是具体的菜单项

4.1 类图和部分源码 4.1.1 MenuComponent.h

#include #include #include using std::cout;using std::endl;using std::string;using std::vector;class MenuComponent{public: virtual void add(MenuComponent *menuComponent); virtual void remove(MenuComponent *menuComponent); virtual MenuComponent *getChild(int i); virtual string getName(); virtual string getDescription(); virtual double getPrice(); virtual bool isVegetarian(); virtual void print(); virtual ~MenuComponent();};

4.1.2 MenuItem.h

#include "MenuComponent.h"class MenuItem:public MenuComponent{public: MenuItem(string name,string description,bool vegetarian,double price); virtual string getName()override final; virtual string getDescription()override final; virtual double getPrice()override final; virtual bool isVegetarian()override final; virtual void print()override final; virtual ~MenuItem();private: string name; string description; bool vegetarian; double price;};

4.1.3 Menu.h

#include "MenuComponent.h"class Menu:public MenuComponent{public: Menu(string name,string description); virtual void add(MenuComponent *menuComponent)override final; virtual void remove(MenuComponent *menuComponent)override final; virtual MenuComponent *getChild(int i)override final; virtual string getName()override final; virtual string getDescription()override final; virtual void print()override final; virtual ~Menu();private: string name; string description; vector menuComponents;};

4.1.4 Waitress.h

#include "MenuComponent.h"class Waitress{public: Waitress(MenuComponent *allMenus); void printMenu(); virtual ~Waitress();private: MenuComponent *allMenus;};

4.1.5 main.cpp

#include #include "MenuComponent.h"#include "Menu.h"#include "Waitress.h"#include "MenuItem.h"using namespace std;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( "Hot Dog", "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;}

5、组合迭代器