C++ Singleton

main.cpp

#include <iostream>
#include "singleton.h"

int main()
{
	std::cout << "Hello World!" << std::endl;
	std::cout << Singleton::instance().singletonMethod() << std::endl;
}

singleton.cpp

#include <iostream>
#include "singleton.h"

Singleton::Singleton(const char* message) {
	std::cout << "Singleton Initialized" << std::endl;
	this->message = message;
}
Singleton::~Singleton() {
	this->message = "If you see this you have threads that are still running after the singleton is destroyed";
	std::cout << "Singleton destroyed" << std::endl;
}
const char* Singleton::singletonMethod() {
	return message;
}

Singleton& Singleton::instance() {
	static Singleton theInstance("My message from singleton constructor");
	return theInstance;
}

singleton.h

#pragma once

class Singleton {
private:
	const char* message;
	Singleton(const char* message);
	~Singleton();
public:
	static Singleton& instance();
	const char* singletonMethod();
};