Design Patterns–Part 1

It has been a unfulfilled dream for me to read design patters.  So started with a couple of videos from YouTube to understand it better. With that I am going to use these patterns in a embedded C++ program some way or another.

Strategy Pattern


Example 1

 

#include <iostream>

using namespace std;

// this is going to be injected to the main class
class Algorithm {
public:
    // abstract class
    virtual void action() =0;
    virtual ~Algorithm() {
    }
};

class Algo1 : public Algorithm {
public:
    void action() {
        cout << "Algo1 action " << endl;
    }

};

class Algo2 : public Algorithm {
public:
    void action() {
        cout << "Algo2 action " << endl;
    }

};


class MainClass {
public:
    // no return type means a constructor
//    MainClass( Algorithm * alg) {
//        this->myAlgo = alg;
//    }
    virtual ~MainClass(){
    }
    Algorithm *myAlgo;
    void act()
    {
        myAlgo->action();
    }
    void setAction(Algorithm * alg) {
        this->myAlgo = alg;
    }
    virtual void display() = 0; // pure virtual function


};

class SubClass : public MainClass {
public:
    SubClass() {
        myAlgo = new Algo1();
    }
    void display() {
        cout << "display" << endl;
    }
};


int main()
{
    MainClass *m= new SubClass();
    m->display();
    m->act();
    m->setAction(new Algo2);
    m->act();

    cout << "Hello world!" << endl;

    return 0;
}

Output

display
Algo1 action
Algo2 action
Hello world!

Process returned 0 (0x0)   execution time : 0.025 s
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