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;
}