Question

I am looking over some open source code and they listed some strange instance in a class defined as:

Obj *&obj;

I had no idea that was possible! What does that mean or even do? The pointer and reference symbols should counteract in my opinion. But maybe it does something special I do not know about?

Looking in the code, they use it as if the instance was a pointer. ie: obj->method(). So then why did they include the &?

Answer 1

That is reference to a pointer. Think in this way:

A *pa = new A(); //pa is pointer to A

A * & rpa = pa; //rpa is reference to pa

rpa = nullptr;  //it modifies pa as well

if ( pa == nullptr )
{
     std::cout << "pa is nullptr" << std::endl;
}

It will print “pa is nullptr” on the console.

If you find A * & difficult to read, then you can use typedef as:

typedef A* PA;

PA & rpa = pa; //same as before