CODEWITHSUNDEEP
c++
hamad khan
hamad khan

Reputation: 11

counting of references of an object

I'm feeling confusion that is there any way to count the reference of an object of the class? 

class A
{
  public :
    A(){}
}

int main()
{
  A obj;
  A * ptr1 = &obj;
  A * ptr2 = &obj;
  A * ptr3 = &obj; 
}

now how i'll be able to know that my object obj is referenced by three pointers.

Upvotes: 0

Views: 80

Answers (2)

Eric Finn
Eric Finn

Reputation: 8985

Raw pointers do not do reference-counting. You would need to either implement a reference-counting smart pointer class yourself, or use an already existing one, such as std::shared_ptr.

shared_ptr allows you to access its reference count with the use_count() member function.

For example:

#include <memory>
#include <iostream>

class A
{
  public :
    A(){}
}

int main()
{
  //Dynamically allocate an A rather than stack-allocate it, as shared_ptr will
  //try to delete its object when the ref count is 0.
  std::shared_ptr<A> ptr1(new A());
  std::shared_ptr<A> ptr2(ptr1);
  std::shared_ptr<A> ptr3(ptr1);
  std::cout<<"Count: "<<ptr1.use_count()<<std::endl; //Count: 3
  return 0;
}

Upvotes: 4

Nick
Nick

Reputation: 25799

Only if you implement it yourself. If you come from a C# or Java (or other managed language) then this can be a difficult concept.

You would be better using one of the standard pointer types provided by C++11 or Boost.

For example, shared_ptr<T> will keep a count of all the 'references' to your objects and manage the lifecycle. unique_ptr<T> will only allow a single pointer to your object.

Upvotes: 2

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