我可以使用C ++中的指针更改静态类成员变量的值吗？

Question

I'm trying to change the value of a static class member variable by returning a pointer to main via an in-class function - the script isn't working and I've tried a few different things, so I decided to reach out for some help. Any ideas, or more efficient ways to do what I'm trying to do?

#include <iostream>

using namespace std;

class container
{
public:
    int accstatint()
    {
        int *ptr=&container::statint;
        return *ptr;
    }
private:
    static int statint;
};
int container::statint=0;

int addone(int *n)
{
    return *n++;
}

int main()
{
    container obj;
    int *ptr=obj.accstatint();
    addone(*ptr);
    cout<<*ptr;
}

Answer 1

int accstatint()
{
    int *ptr=&container::statint;
    return *ptr;
}

This is returning a copy of the int , which means you cannot modify it. You need to return a reference (or pointer) to the int instead:

int& getStatInt() const { return container::statint; }

If you truly want to use a pointer, you can with this (but there's no advantage and you should prefer to use a reference):

int* getStatIntP() { return &container::statint; }

Now you can update the integer:

int main()
{
    container c;
    std::cout << c.getStatInt() << "\n"; // 0
    auto& ref = c.getStatInt();
    ref += 2;
    std::cout << c.getStatInt() << "\n"; //2
}

But all this begs the question: why do you require an object of the class to modify this? Why isn't it just public ? I mean anyone can modify it via your class anyway, so why not just allow direct access to the int to modify. And if you're doing that, what is the purpose of it in the first place? You might want to have a static int in your class to keep track of how many instances of the class are constructed, but you wouldn't allow outside access to it. I can't help you with this without knowing what you're trying to do, you need to think about what your class is and what it does.

Answer 2

While a simple wrapper function would work:

int& acc_staticint() { return staticint; }

You could create a getter and setter, or, since you're effectively making the variable public anyway, you could just do that and then refer to container::staticint .