Head First 设计模式——chapter3 装饰者模式C++实现_C

设计原则：

开闭原则：对扩展开放，对修改关闭。

使得设计具有d性可以应对改变，可以接受新的功能来应对改变需求。

不需要每个地方都遵循，而是在设计最有可能改变的地方应用开闭原则。

eg: 观察者模式，通过加入新的观察者，可以扩展主题对象，而不需向主题中添加代码。

装饰者模式：

动态地将责任附加到对象上，若要扩展功能，装饰者提供了比继承更有d性的替代方案。

装饰类继承自超类，继承是为了有正确的类型，而非继承超类的行为。

#include
#include
#include
#include 
#include 

//饮料抽象类
class Beverage {
public:
	virtual ~Beverage() {};
	virtual std::string getDescription() = 0;
	virtual double cost() = 0;
protected:
	std::string description;
	
};
//调料装饰者类
class Condimentecorator :public Beverage {
public:
	virtual ~Condimentecorator() {};
	virtual std::string getDescription() = 0;
};

//espresso 饮料类
class Espresso :public Beverage {
public:
	Espresso() :Beverage()
	{
		description = "Espresso";
	}
	std::string getDescription() { return description; }
	double cost() 
	{
		return 1.99;
	}
};

//houseblend 饮料类
class HouseBlend :public Beverage {
public:
	HouseBlend() :Beverage()
	{
		description = "HouseBlend";
	}
	std::string getDescription() { return description; }
	double cost() 
	{
		return 0.89;
	}
};

//DarkRoast 饮料类
class DarkRoast :public Beverage {
public:
	DarkRoast() :Beverage()
	{
		description = "DarkRoast";
	}
	std::string getDescription() { return description; }
	double cost() 
	{
		return 0.99;
	}
};

//Decat 饮料类
class Decat :public Beverage {
public:
	Decat() :Beverage()
	{
		description = "Decat";
	}
	std::string getDescription() { return description; }
	double cost()
	{
		return 1.05;
	}
};

//Mocha调料装饰者
class Mocha :public Condimentecorator {

public:
	Mocha(std::shared_ptr be) :Condimentecorator(), beverage(be) {}
	std::string getDescription() 
	{
		return (beverage->getDescription() + " Mocha");
	}
	double cost()
	{
		return 0.2 + beverage->cost();
	}

public:
	std::shared_ptr beverage;
};

//Soy调料装饰者
class Soy :public Condimentecorator {
public:
	Soy(std::shared_ptr be):Condimentecorator(),beverage(be){}
	std::string getDescription()
	{
		return (beverage->getDescription() + " Soy");
	}
	double cost()
	{
		return 0.15 + beverage->cost();
	}
public:
	std::shared_ptr beverage;
};

//Whip调料装饰者
class Whip :public Condimentecorator {
public:
	Whip(std::shared_ptr be) :Condimentecorator(), beverage(be) {}
	std::string getDescription()
	{
		return (beverage->getDescription() + " Whip");
	}
	double cost()
	{
		return 0.10 + beverage->cost();
	}
public:
	std::shared_ptr beverage;
};

int main()
{
	std::shared_ptr beverage (new Espresso());
	std::cout << beverage->getDescription()<<" costs: "<cost() << std::endl;

	std::shared_ptr beverage2(new DarkRoast());
	std::cout << beverage2->getDescription() << " costs: " << beverage2->cost() << std::endl;

	beverage2 = std::shared_ptr(new Mocha(beverage2));
	std::cout << beverage2->getDescription() << " costs: " << beverage2->cost() << std::endl;

	beverage2 = std::shared_ptr(new Mocha(beverage2));
	std::cout << beverage2->getDescription() << " costs: " << beverage2->cost() << std::endl;

	beverage2 = std::shared_ptr(new Whip(beverage2));
	std::cout << beverage2->getDescription() << " costs: " << beverage2->cost() << std::endl;
	auto it = new Whip(beverage2);
	std::cout << it->cost() << " " << it->getDescription() << std::endl;
	std::cout << it->beverage->cost() << " " << it->beverage->getDescription() << std::endl;
	



	/*
	  Beverage *beverage3 = new HouseBlend();
    beverage3 = new Soy(beverage3);
    beverage3 = new Mocha(beverage3);
    beverage3 = new Whip(beverage3);
    cout << beverage3->getDescription() << " $" << beverage3->cost() << endl;
*/
	system("pause");
}