Strategy

(史帝芬, idealist@gcn.net.tw, 2003/11/07)

• Java

Chess.java
package tw.idv.idealist.patterns.strategy;

public class Chess {
　private Strategy strategy;
　private String name;

　public Chess(String name, Strategy strategy) {
　　this.name = name;
　　this.strategy = strategy;
　}

　public int nextHand() {
　　return strategy.nextHand();
　}
}

Strategy.java
package tw.idv.idealist.patterns.strategy;

public interface Strategy {
　public int nextHand();
}

StrategyA.java
package tw.idv.idealist.patterns.strategy;

public class StrategyA implements Strategy {

　public int nextHand() {
　　System.out.println("Strategy A");
　　return 1;
　}
}

StragegyB.java
package tw.idv.idealist.patterns.strategy;

public class StrategyB implements Strategy {

　public int nextHand() {
　　System.out.println("Strategy B");
　　return 2;
　}
}

StrategyC.java
package tw.idv.idealist.patterns.strategy;

public class StrategyC implements Strategy {

　public int nextHand() {
　　System.out.println("Strategy C");
　　return 3;
　}
}

Main.java
package tw.idv.idealist.patterns.strategy;

import java.util.*;

public class Main {
　public static void main(String[] args) {
　　Chess man = null;

　　Random rand = new Random();
　　switch (rand.nextInt(3)) {
　　case 0:
　　　man = new Chess("Steven", new StrategyA());
　　　break;
　　case 1:
　　　man = new Chess("Michael", new StrategyB());
　　　break;
　　case 2:
　　　man = new Chess("Kevin", new StrategyC());
　　　break;
　　}

　　man.nextHand();
　}
}



• C++

Chess.h
#ifndef __CHESS_H
#define __CHESS_H

#include <stdio.h>

template <class S>
class Chess {
private:
　S* ss;
public:
　Chess(S* s) { ss = s; };
　void nextHand() { ss->nextHand(); };
};

#endif

Strategy.h
#ifndef __STRATEGY_H
#define __STRATEGY_H

#include <stdio.h>

class Strategy {
public:
　virtual void nextHand() { printf("super Strategy\n"); };
};

#endif

StrategyA.h
#ifndef __STRATEGY_A_H
#define __STRATEGY_A_H

#include <stdio.h>
#include "Strategy.h"

class StrategyA: public Strategy {
public:
　void nextHand() { printf("Strategy A\n"); };
};

#endif

StrategyB.h
#ifndef __STRATEGY_B_H
#define __STRATEGY_B_H

#include "Strategy.h"
#include

class StrategyB: public Strategy {
public:
　void nextHand() { printf("Strategy B\n"); };
};

#endif

StrategyC.h
#ifndef __STRATEGY_C_H
#define __STRATEGY_C_H

#include "Strategy.h"
#include

class StrategyC: public Strategy {
public:
　void nextHand() { printf("Strategy C\n"); };
};

#endif

MAIN.CPP
#include <time.h>

void main()
{
　Strategy* s;
　srand( (unsigned)time( NULL ) );
　switch (rand() % 3) {
　case 0:
　　s = new StrategyA();
　　break;
　case 1:
　　s = new StrategyB();
　　break;
　case 2:
　　s = new StrategyC();
　　break;
　}
　Chess man(s);
　man.nextHand();
}

說明
上面的範例程式雖然還是有Strategy class，其實這個class可以拿掉，因為已經有template，透過template就可以達到多型了。