C++ Tutorial Index

C++ Tutorial C++ History C++ Installation C++ First Program C++ cin and cout C++ Data type C++ Variable C++ operator C++ Keywords

C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++ Returning Multiple Values from a Function using Tuple and Pair in C++ wcscpy(), wcslen(), wcscmp() Functions in C++

Upcasting and Downcasting in C++

With the help of various examples in the C++ programming language, this section will cover Upcasting and Downcasting. Upcasting and downcasting, on the other hand, are two forms of object typecasting. Consider the Parent and Child classes, which have two types of objects, parent_objct and child_objct, which can be cast into Parent to Child and Child to Parent using C++ programming's Upcasting and Downcasting.

Casting in C++ :

When transforming one type of objects to another, the phrase "casting" is commonly used in programming. It's essentially a "forced conversion", in which you change one type to another manually.

Example :

float x = 7.68;
int y;
 
y = (int)x;

In the above example, we were able to assign a value to y by casting x into an int, despite the fact that y is an int. The float value of x, 7.68 loses all of its digits that are placed after the decimal point and is transformed to an int.

In C++, we may use pointer references to build a "is a" relationship between the parent and child classes. There are two main kinds of casting that may be done:

  • Upcasting
  • Downcasting

Upcasting in C++ :

Upcasting is the process of creating the pointer or reference of the derived class from the pointer or reference of the base class. When compared to downcasting, upcasting is a safer option. It enables public inheritance, which allows a reference to be automatically cast from one class to the other without the need for an explicit typecast. Upcasting creates an is-a relationship between base and derived classes by default.

Base *pntr = &derived_objct; 

The derived class can inherit all of the base class attributes, including data members and the member function, and use the derived class object to run the function, just like a base object.

When a derived class object is provided by the value as a base class object, upcasting can result in object slicing.

Whenever we send out a message to an object that has a virtual member function, the object will perform the proper thing, even if upcasting is used.

Example :

#include <iostream> // std::cout
using namespace std;


class Base 
{
public:
    void baseFunc() 
    {
        cout<<"Base Function!"<<endl;
    }
};


class Derived: public Base 
{
public:
    void derivedFunc()
    {
        cout<<"Derived Function!"<<endl;
    }
};


int main() 
{ 
    Derived dObjct;


//Upcasting – Here, the implicit upcasting is allowed
    Base *bPntr = &dObjct;


    bPntr -> baseFunc();


    return 0; 
}

Output :

Base Function!

Explanation :

In the above example, we explained the concept of upcasting. We used a public base class with a void function called baseFunc(). Then we created a derived class from the public base class having a function called derivedFunc(). Then we used implicit upcasting, using a base pointer bPntr pointing towards the derived object dObjct and resulting in the calling of baseFunc().

Downcasting in C++ :

Downcasting is the opposite of upcasting. Upcasting is the polar opposite of downcasting. It changes the value of a base class pointer to a derived class pointer. Manual downcasting is a requirement. It implies we’ll have to define a type cast explicitly.

The explanation for this limitation is that in most circumstances, the is-a connection is not symmetric. The class member procedures that utilised such data members would not really be applicable to the base class if a derived class added additional data members. It is not as safe to downcast as it is to upcast. A downcast is only safe if the object being referenced at runtime is indeed a derived class object.

Derived *d_pntr = &b_objct;

Example :

#include <iostream> // std::cout
using namespace std;


class Base 
{
public:
    void baseFunc() 
    {
        cout<<"Base Function!"<<endl;
    }
};


class Derived: public Base 
{
public:
    void derivedFunc()
    {
        cout<<"Derived Function!"<<endl;
    }
};


int main() 
{ 
    Base bObjct;


// explicit type casting is required here
    Derived *dPntr = (Derived *) &bObjct;
    dPntr -> derivedFunc();


    return 0; 
}

Output :

Derived Fun

Explanation :

In the above example, we explained the concept of downcasting. We used a public base class with a void function called baseFunc(). Then we created a derived class from the public base class having a function called derivedFunc(). Then we used explicit type casting, using a derived pointer dPntr pointing towards the base object bObjct and resulting in the calling of derivedFunc().



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