Exceptions on c++ - c++

Question

I have this:
// exception::what
#include <iostream> // std::cout
#include <exception> // std::exception
struct ooops : std::exception {
const char* what() const noexcept {return "Ooops!\n";}
};
class A: std::exception{
public:
int tt;
int getTT(int rr){
if (rr ==5) throw ooops();
return rr;
};
};
int main () {
try {
A testA;
int ww = testA.getTT("kkk");
std::cout << ww << std::endl;//throw ooops();
} catch (std::exception& ex) {
std::cout << ex.what();
}
return 0;
}
I want to call getTT() with the string above and I want to throw My Exception message instead the default one. I know that If I overload a method from Exception class I will be ok but I am asking if there is a more easy way to do it.I am reading the documentation on Exceptions but I can't find something useful.

Answer 1

You can throw any object. you don't have to inherit from std::exception
#include <iostream>
class A{
public:
int tt;
int getTT(int rr){
if (rr ==5) throw "ooops";
return rr;
};
};
int main () {
try {
A testA;
int ww = testA.getTT(5);
std::cout << ww << std::endl;//throw ooops();
} catch (const char* exc) {
std::cout << exc;
}
return 0;
}
And If you don't know the type of the exception, you can use ..., as follows
#include <iostream>
class A{
public:
int tt;
int getTT(int rr){
if (rr ==5) throw "ooops";
return rr;
};
};
int main () {
try {
A testA;
int ww = testA.getTT(5);
std::cout << ww << std::endl;//throw ooops();
} catch (...) {
std::cout << "exception has been thrown";
}
return 0;
}

Answer 2

Your ooops class should derive from
std::runtime_error instead, which takes a user-defined string as input and overrides what() for you to return that string.
There are other mistakes in your code, too. A should not derive from std::exception. And A::getTT() takes an int as input, but you are trying to pass it a string literal (const char[4]) instead.
Try this instead:
#include <iostream>
#include <stdexcept>
#include <string>
struct ooops : std::runtime_error {
ooops(const std::string &what_arg = "Ooops!")
: runtime_error(what_arg)
{
}
};
class A {
public:
int tt;
int getTT(int rr) const {
if (rr == 5) throw ooops("rr can't be 5");
return rr;
}
};
int main () {
try {
A testA;
int ww = testA.getTT(5);
std::cout << ww << std::endl; // throw ooops();
}
catch (const std::exception& ex) {
std::cout << ex.what() << std::endl;
}
return 0;
}