10.5. Using the this Pointer

We’ve seen that an object’s member functions can manipulate the object’s data. How do member functions know which object’s data members to manipulate? Every object has access to its own address through a pointer called this (a C++ keyword). The this pointer is not part of the object itself—i.e., the memory occupied by the this pointer is not reflected in the result of a sizeof operation on the object. Rather, the this pointer is passed (by the compiler) as an implicit argument to each of the object’s non-static member functions. Section 10.6 introduces static class members and explains why the this pointer is not implicitly passed to static member functions.

Objects use the this pointer implicitly (as we’ve done to this point) or explicitly to reference their data members and member functions. The type of the this pointer depends on the type of the object and whether the member function in which this is used is declared const. For example, in a nonconstant member function of class Employee, the this pointer has type Employee * const (a constant pointer to a nonconstant Employee object). In a constant member function of the class Employee, the this pointer has the data type const Employee * const (a constant pointer to a constant Employee object).