< Previous | Contents | Next >
Just as you dereference an iterator to access the object to which it refers, you dereference a pointer to access the object to which it points. You accomplish the dereferencing the same way—with *, the dereference operator. I put the dereference operator to work with the following line, which displays 1000 because *pScore accesses the value stored in score.
cout << "*pScore is: " << *pScore << "\n\n"; //value pointed to by pointer
Remember, *pScore means, “the object to which pScore points.”
Tra p
Don’t dereference a null pointer because it could lead to disastrous results.
Next, I add 500 to score with the following line.
score += 500;
When I send score to cout, 1500 is displayed, as you’d expect. When I send
*pScore to cout, the displayed once more.
contents of
score
are
again
sent
to cout, and 1500 is
Understanding Pointer Basics 229
Next, I add 500 to the value to which pScore points with the following line.
*pScore += 500;
Because pScore points to score, the preceding line of code adds 500 to score. Therefore, when I next send score to cout, 2000 is displayed. Then, when I send
*pScore to cout.. .you guessed it, 2000 is displayed again.
Tra p
Don’t change the value of a pointer when you want to change the value of the object to which the pointer points. For example, if I want to add 500 to the int that pScore points to, then the following line would be a big mistake.
pScore += 500;
The preceding code adds 500 to the address stored in pScore, not to the value to which pScore originally pointed. As a result, pScore now points to some address that might contain anything. Dereferencing a pointer like this can lead to disastrous results.
