my 42 cpp piscine

in this module we are going to learn about exception classes, how to use them and how to create our own exception classes

first of all we are goint to talk about the stander exception class std::exception, it is the base class for standard exception defined in the header <exceprion> defined as

    class exception {
        public:
            exception () throw();
            exception (const exception&) throw();
            exception& operator= (const exception&) throw();
            virtual ~exception() throw();
            virtual const char* what() const throw();
}

the keyword throw() is used after all member functions to ensure that the member function won't be throwing an exception while handling an exception.

std::exception

std::bad_alloc

std::bad_cast

std::bad_exception

std::bad_typeid

std::logic_error

std::domain_error

std::invalid_argument

std::length_error

std::out_of_range

std::runtime_error

std::overflow_error

std::range_error

std::underflow_error

to make our exception class we have to derive it publicly from std::exception

#include <exception>

class GradeTooHighExceptionClass : std::exception{

    public:
        const char*   what() const throw() {
            return "your error message";
        };
};

then we have to overload the what() member function , the function to describe what's happening

to throw an exception we use the keyword throw

to catch it we use try catch syntax, example bellow.

   void myFunction(int grade)
{
   if (grade < 0)
       throw GradeTooHighExceptionClass;
   else
       std::cout << "all good" << std::endl;
}

int main()
{
   try {
       myFunction(-1);
   } catch (std::exception &e)
   {
       std::cout << e.what() << std::endl;
   }
}

int the function above if the grade in less than 0 we will throw and exception, than in the main function we give myFunction -1 as argument than we catch it using the keyword catch. our programme will print your error message followed by a new line.

if we use a positive value of grade the function will run and no exception will be thrown, our programme will print all good followed by a new line.