Properly deleting a singleton

Question

I have the following code:

MyClass.h:

static MyMutex instanceMutex;
static MyClass* getInstance();
static void deleteInstance();

MyClas

Answer 1

In one project we inherited from some external company I've seen a whole nightmare class of errors caused by someone deleting the singleton. Perhaps in your rare case deleting the singleton doesn't have any side effects for the whole application, as you can be sure there is no instance of this singleton at use, but, generally, it's an excellent example of bad design. Someone could learn from your example and it would be a bad - even harmful - lesson. In case you need to clean up something in the singleton when the application exit, use the pattern ith returning reference to the singleton, like in example:

#include 

using namespace std;

class singleton {
    private:
        singleton() {
            cout << "construktor\n";
        }
        ~singleton() {
            cout << "destructor\n";
        }
    public:
        static singleton &getInstance() {
            static singleton instance;
            cout << "instance\n";
            return instance;
        }
        void fun() {
            cout << "fun\n";
        }
};


int main() {
    cout << "one\n";
    singleton &s = singleton::getInstance();
    cout << "two\n";
    s.fun();
    return 0;
}