C++ -- How to overload operator+=?

Question

Given the following code snippet,

class Num
{
public:
    Num(int iNumber = 0) : m_iNumber(iNumber) {}

    Num operator+=(const Num& rhs)
    {
        this->m_iNumber = (this->m_iNumber + rhs.m_iNumber);
        return *this;
    }
private:
    int m_iNumber;
};

//===========================================================
int _tmain(int argc, _TCHAR* argv[])
{
    Num a(10);

    Num b(100);

    b += a;

    return 0;
}

I would like to know how to correctly overload the operator+=.

Questions:

1. How to define the signature of this operator? Specially, what should be used for the return value?

2. How to implement the function body?

3. How to use this overload operator?

I have provided a solution as above but I have concerns that it is not correct.

question from:https://stackoverflow.com/questions/4581961/c-how-to-overload-operator

Answer 1

Returning by reference would be better

Num& operator+=(const Num& rhs){

      this->m_iNumber += rhs.m_iNumber;
      return *this;
}