The keyword this

The keyword this represents a pointer to the object whose member function is being executed. It is a pointer to the object itself.

One of its uses can be to check if a parameter passed to a member function is the object itself. For example,

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

// this #include using namespace std; class CDummy { public: int isitme (CDummy& param); }; int CDummy::isitme (CDummy& param) { if (&param == this) return true; else return false; } int main () { CDummy a; CDummy* b = &a; if ( b->isitme(a) ) cout << "yes, &a is b"; return 0; }

yes, &a is b

It is also frequently used in operator= member functions that return objects by reference (avoiding the use of temporary objects). Following with the vector's examples seen before we could have written an operator= function similar to this one:

1 2 3 4 5 6

CVector& CVector::operator= (const CVector& param) { x=param.x; y=param.y; return *this; }

In fact this function is very similar to the code that the compiler generates implicitly for this class if we do not include an operator= member function to copy objects of this class.