模板方法模式

模板方法模式：在一个方法中定义一个算法的骨架，而将一些步骤延迟到子类中。模板方法使得子类可以在不改变算法结构的情况下，重新定义算法的某些步骤。还可以使用钩子对可选部分进行判断。

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

class CaffeineBeverage
{
public:
	void prepareRecipe()
	{
		boilWater();
		brew();
		pourInCup();
		addCondiments();
	}
	virtual void brew(){}
	virtual void addCondiments(){ }
	void boilWater()
	{
		cout << "Boiling water "<< endl;
	}
	void pourInCup()
	{
		cout << "Pouring into cup" << endl;
	}
};

class Tea : public CaffeineBeverage
{
public :
	virtual void brew()
	{
		cout << "Steeping the tea" << endl;
	}
	virtual void addCondiments()
	{
		cout << "Adding Lemon" << endl;
	}
};

class Coffee : public CaffeineBeverage
{
public: 
	virtual void brew()
	{
		cout << "Dripping Coffee through filter" << endl;
	}
	virtual void addCondiments()
	{
		cout << "Adding Sugar and Milk" << endl;
	}
};

class CaffeineBeverageWithHook
{
public:
	void prepareRecipe()
	{
		boilWater();
		brew();
		pourInCup();
		if(customerWantCondiments())
		{
			addCondiments();
		}
	}
	virtual void brew() { }
	virtual void addCondiments() { }
	void boilWater()
	{
		cout << "Boiling water" <<endl;
	}
	void pourInCup()
	{
		cout << "Pouring into cup" << endl;
	}
	virtual bool customerWantCondiments()
	{
		return true;
	}
};

class CaffeeWithHook : public CaffeineBeverageWithHook
{
public:
	virtual void brew()
	{
		cout << "Dripping Coffee through filter" << endl;
	}
	virtual void addCondiments()
	{
		cout << "Adding Sugar and Milk" << endl;
	}

	bool customerWantCondiments()
	{
		string answer = getUserInput();
		if(*(answer.c_str()) == 'y' || *(answer.c_str()) == 'Y')
			return true;
		else
			return false;
	}
private:
	string getUserInput()
	{
		string answer = " ";
		cout << "Would you like milk and sugar with your coffee(y/n)?" << endl;
		cin >> answer;
		if(answer == " ")
			return "no";
		return answer;
	}
};

class TeaWithHook : public CaffeineBeverageWithHook
{
public:
	virtual void brew()
	{
		cout << "Steeping the tea" << endl;
	}
	virtual void addCondiments()
	{
		cout << "Adding Lemon" << endl;
	}

	bool customerWantCondiments()
	{
		string answer = getUserInput();
		if(*(answer.c_str()) == 'y' || *(answer.c_str()) == 'Y')
			return true;
		else
			return false;
	}
private:
	string getUserInput()
	{
		string answer = " ";
		cout << " Would you like milk and sugar with your coffee(y/n)?" << endl;
		cin >> answer;
		if(answer == " ")
			return "no";
		return answer;
	}
};

int main()
{
	TeaWithHook* teaHook = new TeaWithHook();
	CaffeeWithHook* caffeeHook = new CaffeeWithHook();
	cout << "\nMaking tea..." << endl;
	teaHook->prepareRecipe();
	cout << "\nMaking coffee..."<< endl;
	caffeeHook->prepareRecipe();

	return 0;
}