前言
最近在学习《Headfirst设计模式》，里面的例子都是Java的。但是我对Java并不熟悉，所以试着用C++来实现书中的例子。
先来看看Duck以及子类
Duck.h
1 #include <iostream>
2 #include "FlyBehavior.h"
3
4 class Duck
5 {
6 private:
7 FlyBehavior *m_p_fly_behavior;
8 public:
9 virtual void quack() { std::cout << "--quack--" << std::endl; }
10 virtual void swim() { std::cout << "--swim--" << std::endl; }
11 virtual void display() { std::cout << "--duck--" << std::endl; }
12
13 virtual void fly() { if ( m_p_fly_behavior) { m_p_fly_behavior->fly(); } };
14 void set_fly_behavior( FlyBehavior *p_fly_behavior) { m_p_fly_behavior = p_fly_behavior; }
15
16 Duck() : m_p_fly_behavior(NULL) {}
17 virtual ~Duck() { if (m_p_fly_behavior) { delete m_p_fly_behavior; } }
18 };
MallardDuck.h
1 #include "Duck.h"
2 #include "FlyWithWings.h"
3
4 class MallardDuck : public Duck
5 {
6 public:
7 void display() { std::cout << "--MallardDuck--" << std::endl; }
8 MallardDuck() { set_fly_behavior( new FlyWithWings() ); }
9 };
RedheadDuck.h
1 #include "FlyWithWings.h"
2 class RedheadDuck : public Duck
3 {
4 public:
5 void display() { std::cout << "--RedheadDuck--" << std::endl; }
6 RedheadDuck() { set_fly_behavior( new FlyWithWings() ); }
7 };
RubberDuck.h
1 #include "FlyNoWay.h"
2
3 class RubberDuck : public Duck
4 {
5 public:
6 void display() { std::cout << "--RubberDuck--" << std::endl; }
7 void quack() { std::cout << "--squeak--" << std::endl; }
8 RubberDuck() { set_fly_behavior( new FlyNoWay() ); }
9 };
再来看看FlyBehavior类及其子类
FlyBehavior.h
1 #include <iostream>
2
3 class FlyBehavior
4 {
5 public:
6 virtual void fly() {};
7 virtual ~FlyBehavior() {};
8 };
FlyWithWings.h
1 #include "FlyBehavior.h"
2
3 class FlyWithWings : public FlyBehavior
4 {
5 public:
6 void fly () { std::cout << "--fly with wings--" << std::endl; }
7 };
FlyNoWay.h
1 #include "FlyBehavior.h"
2
3 class FlyNoWay : public FlyBehavior
4 {
5 public:
6 void fly() { std::cout << "--can not fly--" << std::endl; }
7 };
最后是主函数
main.cpp
1 #include "MallardDuck.h"
2 #include "RedheadDuck.h"
3 #include "RubberDuck.h"
4 #include <vector>
5
6 void test()
7 {
8 std::vector<Duck *> p_ducks;
9 p_ducks.push_back( new MallardDuck() );
10 p_ducks.push_back( new RedheadDuck() );
11 p_ducks.push_back( new RubberDuck() );
12
13 for (std::vector<Duck *>::iterator it = p_ducks.begin(); it < p_ducks.end(); it ++)
14 {
15 std::cout << std::endl;
16 (*it)->display();
17 (*it)->quack();
18 (*it)->swim();
19 (*it)->fly();
20 delete (*it);
21 }
22 }
23
24 int main()
25 {
26 while (true)
27 {
28 test();
29 }
30 }
稍作解释
main函数中死循环的调用test函数的意图是测试以上实现有没有内存泄露。