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I have example code on C++ that describes my solution:

#include <iostream>

class Singleton {
private:
    static Singleton* instance;
    Singleton() {
        std::cout << "Instance created" << std::endl;
    }
    Singleton(const Singleton&);
    Singleton& operator=(Singleton&);
public:
    static Singleton* getInstance();
    static void m1();
    void m2();
};

Singleton* Singleton::instance = 0;

Singleton* Singleton::getInstance() {
  if (!instance) {
        instance = new Singleton();
    }
    return instance;
}

void Singleton::m1() {
    std::cout << "Called m1" << std::endl;
    instance->m2();
}

void Singleton::m2() {
  std::cout << "Called m2" << std::endl;
}

int main() {
    Singleton* singleton = Singleton::getInstance();
    Singleton::m1();
    return 1;
}

Is it correct that I call instance method m2 from static method m1? Doesn't this cause any problems in maintaining and understanding the code, or would it be better to make m2 method also static?

Yehor Bublyk
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    [Retiring the Singleton Pattern: Concrete Suggestions for What to use Instead - Peter Muldoon](https://www.youtube.com/watch?v=K5c7uvWe_hw) – JHBonarius Dec 22 '20 at 13:59
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    Well, if `m1` gets called before `getInstance()`, you'll have obvious problems. – Sam Varshavchik Dec 22 '20 at 14:06
  • Yes, `m1` should do `getInstance()->m2();`.- Your singleton isn't thread safe though. Two threads could create an instance at the same time. If you're going to use a singleton, it's often easier to go with a `static Singleton instance;` and return a reference to that. – Ted Lyngmo Dec 22 '20 at 14:22
  • That is, if I replace ```instance->m2()``` with ```getInstance()->m2()``` and make Meyer's Singleton instead of mine - it will be correct code, @TedLyngmo? – Yehor Bublyk Dec 22 '20 at 14:34
  • @YehorBublyk It'll be safer anyway. I didn't read everything through to find other potential problems. – Ted Lyngmo Dec 22 '20 at 14:36

0 Answers0