Question

Well, I’ve just started to learn Exceptions at college, here is a code that is supposed to throw an exception if an introduced value is out of a range stablished by me…
Thinking and analizing, I think there might me an error with the throws, and some guy tell me in other question that indeed I have not declared any throw…I may have stupid mistakes so sorry for the trouble
Here is my code:

    #include <iostream>
#include <exception>


class ExcepcionRango : public std::exception{
protected:

    ExcepcionRango::ExcepcionRango(){
    }
public:
    virtual const char* lanzarExcepcion()=0;

};

class ExcedeRangoInferior : public ExcepcionRango{
public:
    ExcedeRangoInferior::ExcedeRangoInferior(){
    }
    const char* lanzarExcepcion() throw(){ //throw exception
        return "Value out of minimal range";
    }
};

class ExcedeRangoSuperior : public ExcepcionRango{
public:
    ExcedeRangoSuperior::ExcedeRangoSuperior(){
    }
    const char* lanzarExcepcion() throw(){ //throw exception
        return "value out of maximal range";
    }
};

int obtainValue(int minimo, int maximo){ //obtain value

    int valor; //value
    std::cout<<"Introduce a value between "<<minimo<<" and "<<maximo<<" : "<<std::endl;
    std::cin>>valor;
    return valor;

};

int main(){
    ExcedeRangoSuperior* exS = new ExcedeRangoSuperior();
    ExcedeRangoInferior* exI= new ExcedeRangoInferior();
    int min=3; 
    int max=10;
    int valor=0; //value
    try{
        valor=obtainValue(min,max);
        if(valor<min){

            throw exS->lanzarExcepcion();
        }
        if(valor>max){

            throw exI->lanzarExcepcion();
        }
    }catch(...){
        std::cout<<"Exception: ";
    }

    delete exS;
    delete exI;
    std::cin.get();
}

PD: the functions lanzarExcepcion() are supposed to throw the message if the inserted value is out of range

Answer 1

Since you are using exceptions in the wrong way, I decided to “refactor” your code to show how it’s most usually done:

#include <iostream>
#include <exception>

class ExcepcionRango : public std::exception
{
protected:
    ExcepcionRango::ExcepcionRango()
        { }
};

class ExcedeRangoInferior : public ExcepcionRango
{
public:
    ExcedeRangoInferior::ExcedeRangoInferior()
        { }

    const char *what() const
    {
        return "Valor fuera de rango inferior";
    }
};

class ExcedeRangoSuperior : public ExcepcionRango
{
public:
    ExcedeRangoSuperior::ExcedeRangoSuperior()
        { }

    const char *what()
    {
        return "valor fuera de rango superior";
    }
};

int obtainValue(const int minimo, const int maximo)
{
    int valor; 
    std::cout << "Introduzca un valor entre " << minimo << " y " << maximo << " : " << std::endl;
    std::cin >> valor;

    if (valor < min)
        throw ExcedeRangoInferior();
    else if (valor > max)
        throw ExcedeRangoSuperior();

    return valor;
};

int main()
{
    const int min = 3; 
    const int max = 10;

    int valor;

    try
    {
        valor = obtainValue(min, max);
    }
    catch (ExcepcionRango &exc)
    {
        std::cerr << "Exception: " << exc.what() << std::endl;
    }

    std::cin.get();
}