策略模式

行为模式：

#include <iostream>

class Base
{
    public:
        virtual void show() = 0;
};

class Children1 : public Base
{
    public:
        void show()
        {
            std::cout<<"Children1"<<std::endl;
        }
};

class Children2 : public Base
{
    public:
        void show()
        {
            std::cout<<"Children2"<<std::endl;
        }
};

typedef enum _Enum
{
    ONE = 1,
    TWO = 2,
} MyEnum;

#define CASE(num,classname) case num:obj=new classname();break;
class Context
{
    public:
        Context(MyEnum num)
        :obj(nullptr)
        {
            switch(num)
            {
                CASE(ONE,Children1)
                CASE(TWO,Children2)

                default:
                    break;
            }
        }

        void show()
        {
            obj->show();
        }

        ~Context()
        {
            delete obj;
        }
    
    public:
        Base* obj;// = nullptr;
};

int main()
{
    Context context(ONE);
    context.show();
}

代码非常类似简单工厂模式，只是多了一层封装，解决了 delete 的问题。 简单工厂模式是创建型模式，侧重对象的创建；策略模式是用来封装算法的。使用目的不一样