Counting instances of individual derived classes

Question

I\'d like to be able to count instances of classes that belong in the same class hierarchy.

For example, let\'s say I have this:

class A;
class B: pu         


        

Answer 1

A very crude way would be:

class A
{
public:
    static int m_instanceCount;
    A(bool derivedInstance = false)
    {
        if(! derivedInstance)
        {
            ++m_instanceCount;
        }
    }
    virtual ~A()
    {
        --m_instanceCount;
    }
    virtual int GetInstanceCount()
    {
        return m_instanceCount;
    }
};

int A::m_instanceCount = 0;


class B : public A
{
public:
    static int m_instanceCount;
    B(bool derivedInstance = false): A(true) 
    {
        if(! derivedInstance)
        {
            ++m_instanceCount;
        }
    }
    virtual ~B()
    {
        --m_instanceCount;
    }
    virtual int GetInstanceCount()
    {
        return m_instanceCount;
    }
};

int B::m_instanceCount = 0;


class C : public B
{
public:
    static int m_instanceCount;
    C(): B(true) {++m_instanceCount;}
    virtual ~C()
    {
        --m_instanceCount;
    }
    virtual int GetInstanceCount()
    {
        return m_instanceCount;
    }
};

int C::m_instanceCount = 0;




void main(int argc,char *argv[])
{   
    A* p1 = new A;
    B* p2 = new B;
    C* p3 = new C;
    C* p4 = new C;
    A* p5 = new A;

    delete p5;

    std::cout<GetInstanceCount()<<"\n";
    std::cout<GetInstanceCount()<<"\n";
    std::cout<GetInstanceCount()<<"\n";
}