策略模式

  #include <iostream>

using namespace std;

class StrategyInterface
{
public:
    virtual void execute() = 0;
};

class ConcreteStrategyA: public StrategyInterface
{
public:
    virtual void execute()
    {
        cout << "Called ConcreteStrategyA execute method" << endl;
    }
};

class ConcreteStrategyB: public StrategyInterface
{
public:
    virtual void execute()
    {
        cout << "Called ConcreteStrategyB execute method" << endl;
    }
};

class ConcreteStrategyC: public StrategyInterface
{
public:
    virtual void execute()
    {
        cout << "Called ConcreteStrategyC execute method" << endl;
    }
};

class Context
{
private:
    StrategyInterface *_strategy;

public:
    Context(StrategyInterface *strategy):_strategy(strategy)
    {
    }

    void set_strategy(StrategyInterface *strategy)
    {
        _strategy = strategy;
    }

    void execute()
    {
        _strategy->execute();
    }
};

int main(int argc, char *argv[])
{
    ConcreteStrategyA concreteStrategyA;
    ConcreteStrategyB concreteStrategyB;
    ConcreteStrategyC concreteStrategyC;

    Context contextA(&concreteStrategyA);
    Context contextB(&concreteStrategyB);
    Context contextC(&concreteStrategyC);

    contextA.execute();
    contextB.execute();
    contextC.execute();

    contextA.set_strategy(&concreteStrategyB);
    contextA.execute();
    contextA.set_strategy(&concreteStrategyC);
    contextA.execute();

    return 0;
}