C ++这个类和单例的全局声明有什么好的替代方法吗？

C++ Are there any good alternatives to global declaration of this class and singleton?

本问题已经有最佳答案，请猛点这里访问。

如何在没有singleton的情况下生成此类的单个实例，以及如何声明它，以便另一个类可以在不全局声明的情况下访问它？

请阅读代码(尤其是注释)，以便更好地理解：

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#include <iostream>
#include <vector>

// The only class that will be using this class is Obj...
// There can only be a single instance of ObjManager but how can I do that
// without singleton???
class ObjManager
{
friend class Obj;
int i;
};

// Since I cannot think of a better way of accessing the SAME and ONLY ObjManager, I
// have decided to declare a global instance of ObjManager so every instance of
// Obj can access it.
ObjManager g_ObjManager;

class Obj
{
friend class ObjManager;
public:
void Set(int i);
int Get();
};

void Obj::Set(int i) {
g_ObjManager.i += i;
};

int Obj::Get() {
return g_ObjManager.i;
};

int main() {
Obj first_obj, second_obj;

first_obj.Set(5);
std::cout << second_obj.Get() << std::endl; // Should be 5.
second_obj.Set(10);
std::cout << first_obj.Get() << std::endl; // Should be 15.

std::cin.get();
return 0;
};