How to throw a C++ exception?
Answers
C++ exception handling is built upon three keywords:- try, catch, and throw. throw − A program throws an exception when a problem shows up. This is done using a throw keyword. Catch − A program catches an exception with an exception handler at the place in a program where you want to handle the problem.
Answer:
try: represents a block of code that can throw an exception. catch: represents a block of code that is executed when a particular exception is thrown. throw: Used to throw an exception. Also used to list the exceptions that a function throws, but doesn't handle itself.
Explanation:
#include <iostream>
#include <string>
using namespace std;
class MyException : public exception
{
public:
MyException(const string& msg) : m_msg(msg)
{
cout << "MyException::MyException - set m_msg to:" << m_msg << endl;
}
~MyException()
{
cout << "MyException::~MyException" << endl;
}
virtual const char* what() const throw ()
{
cout << "MyException - what" << endl;
return m_msg.c_str();
}
const string m_msg;
};
void throwDerivedException()
{
cout << "throwDerivedException - thrown a derived exception" << endl;
string execptionMessage("MyException thrown");
throw (MyException(execptionMessage));
}
void illustrateDerivedExceptionCatch()
{
cout << "illustrateDerivedExceptionsCatch - start" << endl;
try
{
throwDerivedException();
}
catch (const exception& e)
{
cout << "illustrateDerivedExceptionsCatch - caught an std::exception, e.what:" << e.what() << endl;
// some additional code due to the fact that std::exception was thrown...
}
catch(const MyException& e)
{
cout << "illustrateDerivedExceptionsCatch - caught an MyException, e.what::" << e.what() << endl;
// some additional code due to the fact that MyException was thrown...
}
cout << "illustrateDerivedExceptionsCatch - end" << endl;
}
int main(int argc, char** argv)
{
cout << "main - start" << endl;
illustrateDerivedExceptionCatch();
cout << "main - end" << endl;
return 0;
}