设计模式之策略模式（使用C++）

#include <iostream>

class Algorithm
{
public:
    virtual void add() = 0;
    virtual void sub() = 0;
};

class AlgorithmA : public Algorithm
{
public:
    virtual void add() override
    {
        std::cout<<"Use A plan to add x and y"<<std::endl;
    }
    virtual void sub() override
    {
        std::cout<<"Use A plan to sub x and y"<<std::endl;
    }
};

class AlgorithmB : public Algorithm
{
public:
    virtual void add() override
    {
        std::cout<<"Use B plan to add x and y"<<std::endl;
    }
    virtual void sub() override
    {
        std::cout<<"Use B plan to sub x and y"<<std::endl;
    }
};

class Context
{
public:
    Context(Algorithm* plan) 
        : _plan(nullptr)
    {
        _plan = plan;
    } 

    ~Context()
    {
        if(_plan)
        {
            delete _plan;
            _plan = nullptr;
        }
    }

public:
    void add()
    {
        _plan->add();
    }
    void sub()
    {
        _plan->sub();
    }

private:
    Algorithm* _plan;
};

int main()
{
    Context* contextA = new Context(new AlgorithmA());
    Context* contextB = new Context(new AlgorithmB());

    contextA->add();
    contextA->sub();

    contextB->add();
    contextB->sub();

    delete contextA;
    delete contextB;

    system("pause");
    return 0;
}

我(Algorithm)有理论创建方法、讲解给各位听(A&B)、但是各位的实际方式不一样(plan)，所以需要使用context进行统一管理。————策略模式。