如何在类中声明一个变量，该变量将跟踪C++[duplicate]创建的对象的计数

Question

如何在类中声明一个变量，该变量将跟踪创建的对象的计数？示例对象obj；obj.object_count()；

Answer 1

您可以使用static类成员存储对象计数。并在类构造函数中增加其值,在析构函数中减少其值。

请查找内联备注：

#include <iostream>
#include <atomic>

class Object
{
public:
    Object()    // Constructor
    {
        // initialize the object
        // ...

        m_objCount++;   // Increase object count when creating object (In constructor)
    }

    Object(const Object& obj)   // Copy constructor
    {
        m_objCount++;
    }

    Object(Object&&) // Move constructor
    {
        m_objCount++;
    }

    ~Object()
    {
        m_objCount--;   // Decrease object count when destroying object
    }

    static int object_count()   // Define a static member function to retrive the count
    {
        return m_objCount;
    }

private:
    static std::atomic_int m_objCount;  // Use static member to store object count, 
                                        // use std::atomic_int to make sure it is thread safe
};

std::atomic_int Object::m_objCount; // Initialize static member

int main()
{
    Object obj;

    // prints "obj count: 1"
    std::cout << "obj count: " << obj.object_count() << std::endl;          // call object_count() with object
    std::cout << "obj count: " << Object::object_count() << std::endl;      // call object_count() with class name
}