How to Throw a Custom Exception in C++? - Coding

In C++, exception handling is done by throwing an exception in a try block and catching it in the catch block. We generally throw the built-in exceptions provided in the <exception> header but we can also create our own custom exceptions.

In this article, we will discuss how to throw a custom exception in C++.

Throwing Custom Exceptions in C++

To throw a custom exception, we first have to create a custom exception class. This class inherits the std::exception class from <exception> header. We override the what() method of this class to provide a custom error message.

The last step is to use this user-defined custom exception in our code. The below method demonstrates how to do it.

C++ Program to Throw a Custom Exception

C++

// C++ program to demonstrate a custom exception class 
  
#include <exception> 
#include <iostream> 
#include <string> 
  
using namespace std; 
  
// Define a new exception class that inherits from 
// std::exception 
class MyException : public exception { 
private: 
    string message; 
  
public: 
    // Constructor accepts a const char* that is used to set 
    // the exception message 
    MyException(const char* msg) 
        : message(msg) 
    { 
    } 
  
    // Override the what() method to return our message 
    const char* what() const throw() 
    { 
        return message.c_str(); 
    } 
}; 
  
// Usage 
int main() 
{ 
    try { 
        // Throw our custom exception 
        throw MyException("This is a custom exception"); 
    } 
    catch (MyException& e) { 
        // Catch and handle our custom exception 
        cout << "Caught an exception: " << e.what() << endl; 
    } 
  
    return 0; 
}

Output

Caught an exception: This is a custom exception

Reffered: https://www.geeksforgeeks.org

C++

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