THECODEPROGRAM

Let's get started.

Firstly, What is Singleton Design Pattern
Singleton Design Pattern provides one global object for all classes. We create a class and its own instance. Singleton class will manage its own instance. Also it provides a global access point. All classes reach this singleton classes via this access point.

#include <QCoreApplication>
#include <iostream>
#include <QString>

using namespace std;

//We create a class with public property
class Configurations{
    public :
        int volume;
        bool notification;
};

Now below we are going to create a Singleton class. Then we are going to create a public instance. We are going to access this singleton class through this instance from all around the program.

//Now create the singleton class
class Singleton {
   static Singleton *instance;
   Configurations *config;

   // initialize the related configuration class at constructor
   Singleton() {
      config = new Configurations();
   }

   //First initialize the instance. All classes will access via this instance
   public:
   static Singleton *getInstance() {
      if (!instance) instance = new Singleton;
      return instance;
   }

   //Getters and setters of related functions of realted configurations
   void setVolume(int vol) { this->config->volume = vol; }
   int getVolume() { return this->config->volume; }

   void setNotification(bool notify) { this->config->notification = notify; }
   bool getNotification() { return this->config->notification; }
};

And then we are going to use getters and setters in singleton class to manage the configurations.

Singleton *Singleton::instance = 0;

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

     system("title Singleton Design Pattern Example - Thecodeprogram");
    cout << "Welcome Singleton Design Pattern Example in QT C++" << endl << endl;

    Singleton *s = s->getInstance();
    s->setVolume(50);
    cout << "Volume level is : " << s->getVolume() << endl;
    s->setNotification(true);
    cout << "Notification sending config is : " << s->getNotification() << endl;

    return a.exec();
}

You can reach the example code on Github : https://github.com/thecodeprogram/TheSingleFiles/blob/master/QSingletonPattern_Example.cpp

That is all in this article.

Burak Hamdi TUFAN