C++ Class & object pointer in c++ programming language

C++ class & object to pointer

1. C++ (Programming Language) Submitted By: T. Hari Tharshini Pointer to Class & Object

2. Pointers Pointers  are variables that store the address of another variable. Instead of holding actual data, they point to the location where the data resides . To declare a pointer, you use the * operator. For instance, to declare an integer pointer : int * p ; This tells the compiler that p is a pointer to an integer. However, this pointer doesn’t yet point to any address.

3. Initializing Pointers After declaration, it's crucial to initialize a pointer before using it. An uninitialized pointer can lead to undefined behavior. You can initialize it with the address of a variable: int x = 10; int * p = & x ; Here, p now contains the address of x. The & operator fetches the address of the variable . It’s called reference operator .

4. Dereferencing Pointers The process of retrieving the value from the address a pointer is pointing to is called  dereferencing . To dereference a pointer, use the * operator again: int y = * p ; // y will be 10, as *p gives the value stored at the address p is pointing to

5. Pointer Types Each pointer in C++ has a specific type: the type of data to which it points. For example, an  int  pointer can only point to an integer, a  float  pointer can only point to a floating-point number, and so forth . Type Pointer Declaration int int* p; float float* f; char char* c;

6. Common Errors With Pointers One common mistake is not initializing a pointer before use. Always ensure a pointer points to a valid location. Another pitfall is going beyond the memory bounds. This can corrupt data or crash the program. int arr [5]; int * p = arr ; // Pointing to the start of the array *( p + 5) = 10; // Error! We’re accessing memory beyond the array's bounds

7. Pointer Arithmetic C++ allows arithmetic operations on pointers. However, one must be cautious while doing so to avoid accessing unintended memory locations. int a = 5, b = 10; int * ptr = & a ; ptr ++; // Now ptr points to b

8. Class Pointers In C++, not only can you have pointers to fundamental data types, but you can also have  pointers to classes . These allow for more dynamic and flexible object handling, especially when dealing with polymorphism and dynamic memory allocation .

9. Declaring Class Pointers When you have a class, declaring a pointer to it is similar to how you declare pointers to basic data types. Given a class named Car, you would declare a pointer to it as follows : class Car { // ... class definition ... }; Car * ptrCar ; After this, ptrCar can point to an instance (object) of the Car class.

10. Initializing And Using Class Pointers To make your pointer useful, you should make it point to an actual object. You can either point it to an existing object or allocate memory dynamically . Car myCar ; ptrCar = & myCar ; // Pointing to an existing object Car * dynamicCar = new Car(); // Dynamically allocating memory for a Car object and pointing to it

11. When accessing members (both data members and member functions) of the class through the pointer, use the arrow (->) operator : ptrCar -> startEngine (); // Calls the startEngine () method of the object pointed to by ptrCar

12. Dynamic Memory And Class Pointers One of the key utilities of class pointers is in dynamic memory allocation. When creating objects at runtime based on program needs, using new and delete becomes essential . Car * dynamicArray = new Car [10]; // Allocates memory for an array of 10 Car objects delete [] dynamicArray ; // Frees up the allocated memory once done Always remember to free up memory after use to prevent memory leaks.

13. Polymorphism And Class Pointers One of the strengths of class pointers lies in  polymorphism . By having a base class pointer point to a derived class object, you can achieve runtime polymorphism . class Base {}; class Derived : public Base {}; Base * bPtr = new Derived(); // Base pointer pointing to derived class object This feature enables more dynamic behavior, especially with overridden functions and virtual functions in C++.

14. Declaring And Initializing Class Pointers Working with objects in C++ often requires understanding how to declare and initialize pointers to those objects. Handling  class pointers  correctly can enable dynamic memory management and more flexible object interactions.

15. Declaration Of Class Pointers A class pointer declaration follows a similar syntax as pointers to basic data types. Let's say we have a class named Robot. A pointer to this class would be : class Robot { // ... class definition ... }; Robot * ptrRobot ; // Declaration of pointer to Robot class

16. Initializing With Existing Objects Often, you might want a pointer to reference an existing object. This can be done using the address-of operator (&): Robot r2d2 ; ptrRobot = & r2d2 ; // ptrRobot now points to r2d2

17. Dynamic Memory Allocation For more dynamic applications, C++ allows for on-the-fly memory allocation using the new keyword. This is especially useful when the number or size of objects needed is unknown at compile time. Robot * dynRobot = new Robot(); // Allocates memory and initializes a new Robot object Always remember, for every new, there should be a corresponding delete to free up the allocated memory: delete dynRobot ; // Frees up the memory

18. Pointers To Class Arrays You can also declare and initialize pointers to arrays of class objects. This is useful for creating collections of objects dynamically: Robot * robotArray = new Robot [5]; // Creates an array of 5 Robot objects // Accessing members of the array robotArray [2 ].activate(); // Activates the third robot in the array Again, remember to free the memory : delete[] robotArray ; // Deletes the entire array

19. The Arrow Operator The  arrow operator (->)  is your primary tool for accessing members of a class via a pointer. This operator is a combination of the dereference (*) operator and the dot (.) operator. Given a class Vehicle: class Vehicle { public : void honk() { // Honking logic } }; Vehicle * ptrVehicle = new Vehicle(); ptrVehicle - >honk(); // Using the arrow operator to access the honk function

20. Accessing Data Members Just as with member functions, data members of a class are also accessed using the arrow operator when working with pointers. class Vehicle { public : int speed ; }; Vehicle * ptrVehicle = new Vehicle(); ptrVehicle - > speed = 60; // Setting the speed data member via pointer

21. Dereferencing And The Dot Operator Though the arrow operator is more common and direct, you can also dereference the pointer and use the dot operator to access class members: (* ptrVehicle ). speed = 50; // Dereferencing the pointer and then using the dot operator This method is less common because it's more verbose, but understanding it underscores the concept that the arrow operator is just a shorthand for this process.

22. Accessing Array Elements Through Pointers If you have a pointer to an array of objects, you can combine pointer arithmetic with member access : Vehicle * fleet = new Vehicle [10]; ( fleet + 3)-> speed = 70; // Accessing the speed of the fourth vehicle in the array It's essential to remember the precedence of operators here. The arrow operator will act before the addition, so using parentheses ensures the correct behavior.