Custom Exceptions

Overview

For domain-specific errors (e.g., `InsufficientFundsException` for a bank), you can create your own exception classes by inheriting from `std::exception`.

Syntax

cpp

#include <exception>

class MyCustomError : public std::exception {
public:
    // Overriding the what() method
    const char* what() const noexcept override {
        return "A highly specific custom error occurred!";
    }
};

try {
    throw MyCustomError();
} catch (const std::exception& e) {
    cout << e.what();
}

Common Pitfalls

Forgetting to inherit from `std::exception`. While you can throw any class, inheriting from `std::exception` ensures your error is caught by generic `catch (const std::exception&)` blocks.

Interview Tips

The `noexcept` keyword in the `what()` method signature promises the compiler that the `what()` function itself will never throw an exception. This is required when overriding `std::exception::what()`.

Real-World Example

Custom exception for a banking application.

example

cpp

#include <iostream>
#include <exception>
using namespace std;

class InsufficientFunds : public exception {
public:
    const char* what() const noexcept override {
        return "Transaction Failed: Not enough money in account.";
    }
};

void withdraw(int balance, int amount) {
    if (amount > balance) {
        throw InsufficientFunds();
    }
    cout << "Withdrawal successful.\n";
}

int main() {
    try {
        withdraw(100, 500);
    } catch (const InsufficientFunds& e) {
        cout << e.what() << endl;
    }
    return 0;
}

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