Method模式

1,总结:
基类中包含一个主方法,主方法由若干个子方法组成.
各个子方法的实现由具体的继承类各自实现.
包含一个钩子,决定某些可选方法是否实施.

2,贴个实例代码:

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

class CaffeineBeverage
{
public:
    virtual ~CaffeineBeverage() = 0;
	virtual void prepareRecipe()
	{
		boilWater();
		brew();
		pourInCup();
		addCondiments();
	}
protected:
    virtual void brew() const = 0;
 	virtual void addCondiments() const = 0;
 	void boilWater() const
 	{
		cout << "Boiling water" << endl;
	}
 	void pourInCup() const
 	{
		cout << "Pouring into cup" << endl;
	}
};
CaffeineBeverage::~CaffeineBeverage() {};

class CaffeineBeverageWithHook
{
public:
    virtual ~CaffeineBeverageWithHook() = 0;
	public: virtual void prepareRecipe()
	{
		boilWater();
		brew();
		pourInCup();
		if( customerWantsCondiments() ) //hook
		{
			addCondiments();
		}
	}
	virtual void brew() const = 0;
	virtual void addCondiments() const = 0;
	virtual void boilWater() const //相同的方法
	{
		cout << "Boiling water" << endl;
	}
	virtual void pourInCup() const //相同的方法
	{
		cout << "Pouring into cup" << endl;
	}
protected:
    virtual bool customerWantsCondiments() const//这里还有个默认的...
	{
		return true;
	}
};
CaffeineBeverageWithHook::~CaffeineBeverageWithHook() {};

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

class CoffeeWithHook : public CaffeineBeverageWithHook
{
public:
    void brew() const
    {
		cout << "Dripping Coffee through filter" << endl;
	}
 	void addCondiments() const
 	{
		cout << "Adding Sugar and Milk" << endl;
	}
	bool customerWantsCondiments() const
	{
		bool value = false;
		string answer = getUserInput();
		if( answer.find('y') != -1 )
		{
			value = true;
		}
		return value;
	}
 	string getUserInput() const
 	{
		string value;
		cout << "Would you like milk and sugar with your coffee (y/n)? " << endl;
		cin >> value;
		return value;
	}
};

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

class TeaWithHook : public CaffeineBeverageWithHook
{
public:
    void brew() const
    {
		cout << "Steeping the tea" << endl;
	}
 	public: void addCondiments() const
 	{
		cout << "Adding Lemon" << endl;
	}
  	bool customerWantsCondiments() const //重载了呀!!!
  	{
		bool value = false;
		string answer = getUserInput();
		if( answer.find('y') != -1 ) {
			value = true;
		}
		return value;
	}
	string getUserInput() const
	{
		string value;
		cout << "Would you like lemon with your tea (y/n)? " << endl;
		cin >> value;
		return value;
	}
};

int main()
{
    /*
	auto_ptr< Tea > tea( new Tea() );
	auto_ptr< Coffee > coffee( new Coffee() );

	cout << endl << "Making tea..." << endl;
	tea->prepareRecipe();

	cout << endl << "Making coffee..." << endl;
	coffee->prepareRecipe();
*/
	//auto_ptr< TeaWithHook > teaHook( new TeaWithHook() );
	auto_ptr< CoffeeWithHook > coffeeHook( new CoffeeWithHook() );

    TeaWithHook* teaHook = new TeaWithHook();
	cout << endl << "Making tea..."<< endl;
	teaHook->prepareRecipe();

	cout << endl << "Making coffee..."<< endl;
	coffeeHook->prepareRecipe();
    return 0;
}