C++ code for implementing Strategy Design Pattern:
"The Strategy design pattern defines a family of algorithms,encapsulates each one,and make then interchangeable.Strategy lets the algorithm vary independently from clients that use it."
Problem Statement: Making Ducks Fly. :)
1: #include<iostream>
2: using namespace std;
3: class FlyBehaviour
4: {
5: public:
6: virtual void fly()=0;
7: };
8: class FlyWithWings:public FlyBehaviour
9: {
10: public:
11: void fly()
12: {
13: cout<<"I'm flying"<<endl;
14: }
15: };
16: class FlyNoWay:public FlyBehaviour
17: {
18: public:
19: void fly()
20: {
21: cout<<"I can't fly..."<<endl;
22: }
23: };
24: class QuackBehaviour
25: {
26: public:
27: virtual void quack()=0;
28: };
29: class Quack:public QuackBehaviour
30: {
31: public:
32: void quack()
33: {
34: cout<<"Quack"<<endl;
35: }
36: };
37: class MuteQuack:public QuackBehaviour
38: {
39: public:
40: void quack()
41: {
42: cout<<"Silence"<<endl;
43: }
44: };
45: class Squeak:public QuackBehaviour
46: {
47: public:
48: void quack()
49: {
50: cout<<"Squeak"<<endl;
51: }
52: };
53: class Duck
54: {
55: protected:
56: FlyBehaviour *flyBehav;
57: QuackBehaviour *quackBehav;
58: public:
59: Duck(){}
60: void swim()
61: {
62: cout<<"All ducks float/swim"<<endl;
63: }
64: virtual void display()=0;
65: void performFly()
66: {
67: flyBehav->fly();
68: }
69: void performQuack()
70: {
71: quackBehav->quack();
72: }
73: void setFlyingBehav(FlyBehaviour *pflyBehav)
74: {
75: flyBehav = pflyBehav;
76: }
77: void setQuackingBehav(QuackBehaviour *pquackBehav)
78: {
79: quackBehav = pquackBehav;
80: }
81: };
82: class MallardDuck:public Duck
83: {
84: public:
85: MallardDuck()
86: {
87: quackBehav = new Quack();
88: flyBehav=new FlyWithWings();
89: }
90: void display()
91: {
92: cout<<"I am real Mallard Duck"<<endl;
93: }
94: };
95: class ModelDuck:public Duck
96: {
97: public:
98: ModelDuck()
99: {
100: quackBehav = new Quack();
101: flyBehav=new FlyNoWay();
102: }
103: void display()
104: {
105: cout<<"I am Model Duck"<<endl;
106: }
107: };
108: class FlyRocketPowered:public FlyBehaviour
109: {
110: void fly()
111: {
112: cout<<"Fly Rocket Powered ==> Zoooom"<<endl;
113: }
114: };
115: class DuckHunter
116: {
117: private:
118: Duck * duckType;
119: public:
120: void SetDuckType(Duck *pDuck)
121: {
122: duckType = pDuck;
123: }
124: void StartHunting()
125: {
126: for(int i=0;i<3;i++)
127: duckType->performQuack();
128: }
129: };
130: int main()
131: {
132: cout<<"*********Hello Duck*********"<<endl;
133: Duck *mallard = new MallardDuck();
134: mallard->display();
135: mallard->performQuack();
136: mallard->performFly();
137: Duck *model = new ModelDuck();
138: model->performFly();
139: model->setFlyingBehav(new FlyRocketPowered());
140: model->performFly();
141: DuckHunter *huntingToy = new DuckHunter();
142: huntingToy->SetDuckType(new MallardDuck());
143: huntingToy->StartHunting();
144: return 0;
145: }
