Pointers To Constants
This article is quite advanced and assumes you have an understanding of C++. If not, please refer to the C++ section of this book!
Pointers To Constants in C++ are pointers that can have their memory address reassigned, but cannot be used to modify the value they point to (just like a standard const variable). The target is flexible, but the pointed-to value cannot be modified!
int someVar = 69;
const int* pointerToConst = &someVar;
// It is illegal to go:
// *pointerToConst = 420;
It offers a few benefits:
- Unlike a const pointer, a pointer to const can be reassigned to point to different memory locations, offering more flexibility in managing the target of the pointer.
- Conveys the programmer’s intent that the pointer itself can be changed, but the data it points to should not be modified through this particular pointer.
- Allows a pointer to point to both const and non-const data. This versatility is useful when you want a single pointer to handle both read-only and read-write scenarios.
- When used in function parameters or class member functions, a pointer to const indicates that the function/method will not modify the input data, offering safer interfaces.
- Allows the compiler to make certain optimizations based on const-correctness, potentially leading to more efficient code.
#include <iostream>
int main()
{
int value = 69;
// Pointer to const int
const int* ptrToConst = &value;
// Can reassign ptrToConst to point to a different integer
int anotherValue = 420;
ptrToConst = &anotherValue;
// Cannot modify the pointed-to value through ptrToConst
// *ptrToConst = 42069; // Error
// Access the value
std::cout << "Value: " << *ptrToConst << std::endl;
return 0;
}