Pointers in

About Pointers

Like many other languages, C++ has pointers. You already know references and pointers are similar, but think of them as a level closer to the inner workings of your computer. Pointers are variables that hold object addresses. They are used to directly interact with objects, enabling dynamic memory allocation and efficient data manipulation in C++.

If you're new to pointers, they can feel a little mysterious but once you get used to them, they're quite straight-forward.

They're a crucial part of C++, so take some time to really understand them. The bare-bone version in this concept is also called dumb pointer or raw pointer. With modern C++ there are also smart pointers, the basic type is not smart at all and you have to handle all the work manually.

Before digging into the details, it's worth understanding the use of pointers. Pointers are a way to share an object's address with other parts of our program, which is useful for two major reasons:

1. Like references, pointers avoid copies and help to reduce the resource-footprint of your program.
2. Unlike references, pointers can be reassigned to different objects.
3. Pointers can also point to a null value, to indicate, that they currently do not point to any object.

General Syntax

A pointer declaration in C++ involves specifying the data type to which the the pointer is pointing, followed by an asterisk (*) and the pointer's name. When pointers are declared, they are not automatically initialized. Without explicit assignment, a pointer typically holds an indeterminate value, often referred to as a "garbage address." While certain compilers might initialize pointers to nullptr, this behavior is not guaranteed across all compilers, so it's essential not to rely on it. It's best practice to explicitly initialize raw pointers and verify their non-null status before utilization to avoid potential issues.

int* ptr{nullptr}; // Declares a pointer and makes sure it is not invalid

To assign the address of a variable to a pointer, you use the address-of operator (&). Dereferencing a pointer is done using the indirection operator (*) operator.

std::string opponent{"Solomon Lane"};
// 'ethan' points to the address of the string opponent
std::string* ethan{&opponent}; 
// Instead of ethan's, the opponent's name address is given to the passPort
std::string passportName{*ethan};

Attention: dereferencing has to be done explicitly, while references just worked like an alias.

Pointer Arithmetic

Pointer arithmetic allows you to perform arithmetic operations on pointers, which is particularly useful when working with arrays. Adding an integer to a pointer makes it point to a different element.

// Stargate Coordinate Code
int gateCode[] = {462, 753, 218, 611, 977};
// 'ptr' points to the first element of 'gateCode'
int* ptr{&gateCode[0]};
// Accesses the third Stargate address through pointer arithmetic
int dialedAddress{*(ptr + 2)}; 
// Chevron encoded! Dialing Stargate address:
openStarGate(dialedAddress);

Accessing member variables

In C++, the -> operator is used to access members of an object through a pointer to that object. It is a shorthand which simplifies accessing members of objects pointed to by pointers. For instance, if ptr is a pointer to an object with a member variable x, instead of using (*ptr).x, you can directly use ptr->x. This operator enhances code readability and reduces verbosity when working with pointers to objects.

Here's a brief example, with a struct Superhero that has a member variable superpower. The main function creates a pointer dianaPrince to a Superhero object (representing Wonder Woman). The -> operator is used to access the member variable superpower, showcasing Wonder Woman's iconic "Lasso of Truth."

struct Superhero {
    std::string superpower;
};

Superhero wonder_woman{};
Superhero* dianaPrince = &wonder_woman;
dianaPrince->superpower = "Lasso of Truth";

// Using the -> operator to access member variable superpower:
std::cout << "Wonder Woman, possesses the mighty " << dianaPrince->superpower;

// Memory cleanup:
delete dianaPrince; 

Pointers vs. references

Pointers and references both enable indirect access to objects, but they differ in their capabilities and safety considerations. Pointers offer the flexibility of changing their target object and can be assigned null. However, this flexibility introduces risks, such as dereferencing null pointers or creating dangling pointers. References, on the other hand, cannot be null and are bound to valid objects upon creation, avoiding these risks. Given their safer nature, references should be preferred over pointers unless the additional functionalities provided by pointers are necessary.

// There is a dark mark bearer, but who is it?
std::string* darkMarkBearer{nullptr};
// It is Bellatrix!
darkMarkBearer = new std::string{"Bellatrix Lestrange"};
// She has been defeated
delete darkMarkBearer;
// Reset pointer to null, symbolizing there is no more darkMarkBearer at the moment
darkMarkBearer = nullptr;