Question

I have the following code

#include <vector>
#include <iostream>

class A{
    private:
    std::vector<int> x;
    A(){
        // here is a code to open and initialize several devices
        // it is allowed to be called once only!!!
        std::cout << "constructor called" << std::endl;
    };

    virtual ~A(){
        // here is a code to close several devices
        // it is allowed to be called once only!!!
        std::cout << "destructor called" << std::endl;
    };


    public:
    static A & getA(){
        static A* singleton = new A;
        std::cout << "singleton got" << std::endl;
        return *singleton;
    };

};


int main(int argc, char** argv){

    A a = A::getA();

    return(0);
}

According to many recommendations the destructor is private to be called once only at end of program.
But i have the compiler error:

Test.cpp: In function 'int main(int, char**)':
Test.cpp:12:10: error: 'virtual A::~A()' is private
Test.cpp:29:19: error: within this context
Test.cpp:12:10: error: 'virtual A::~A()' is private
Test.cpp:29:19: error: within this context

Of cause, I can make constructor and/or destructor public and have no any errors like that. But I need to be sure that both of them are called once and only once.
How?

Answer 1

Better use this method of singleton constructor:

static A* getA(){
    static A singleton;
    std::cout << "singleton got" << std::endl;
    return &singleton;
};

Link for more info is Here