Exception Handling

Even the best-written programs can encounter unexpected situations: a file might be missing, a network connection might fail, or a user might try to divide by zero.

If left unhandled, these runtime errors will cause the program to crash abruptly. Exception Handling provides a structured way to react to exceptional circumstances, transferring control from the point where the error occurred to a designated error handler.

1. The Try, Throw, Catch Keywords

C++ handles exceptions using three keywords:

try: You place the code that might generate an error inside a try block.
throw: When a problem occurs, you use the throw keyword to generate an exception. You can throw primitive types (like int or string), or custom class objects.
catch: The catch block intercepts the thrown exception and executes code to handle the error.

Basic Syntax Example

cpp

#include <iostream>
#include <stdexcept>
using namespace std;
 
int main() {
    double numerator = 10;
    double denominator = 0;
 
    try {
        if (denominator == 0) {
            // Error detected! Throw an exception.
            throw runtime_error("Division by zero error!");
        }
        
        // This line is skipped if an exception is thrown
        cout << "Result: " << (numerator / denominator) << endl;
        
    } catch (const runtime_error& e) {
        // This block catches the exception and handles it gracefully

2. Catching Multiple Types

A single try block can be followed by multiple catch blocks to handle different types of exceptions in different ways.

cpp

try {
    // Code that might throw int, char*, or standard exceptions
} catch (int errorCode) {
    cout << "Caught integer error: " << errorCode << endl;
} catch (const char* errorMsg) {
    cout << "Caught string error: " << errorMsg << endl;
} catch (...) {
    // The "catch-all" handler intercepts any exception not caught above
    cout << "Caught an unknown exception!" << endl;
}

3. Standard Exception Classes

C++ provides a standard library of exceptions under the <stdexcept> header. They all inherit from a base class called std::exception.

Common standard exceptions include:

std::runtime_error: Errors that can only be detected at runtime.
std::out_of_range: Thrown when accessing elements out of bounds (e.g., in a vector).
std::invalid_argument: Thrown when an invalid argument is passed to a function.

Summary

Exceptions provide a way to gracefully handle errors without crashing the program.
Wrap risky code in a try block.
Use throw to signal an error condition.
Use catch blocks to define how to handle specific errors.
The catch(...) block can be used to catch any unknown exception.

Assessed progress

Exception Handling

Exception Handling

1. The Try, Throw, Catch Keywords

Basic Syntax Example

2. Catching Multiple Types

3. Standard Exception Classes

Summary

Key Concepts

Exception

try

throw

catch

Quick Check

Object Oriented Programming

Object Oriented Programming