Exception Catching

[Griffinflame21]

I'm trying to do a try catch in line 21, so if the user types something other than 1, 2, or 3 it will give them an error. This is wrong, so how would I do this correctly?

try
{
cin >> choice;
}
catch(out_of_range)
{
cerr << "An error occurred. Please choose a valid menu item number.";
}

main.cpp

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include "Record.h"
using namespace std;

class Recordsbook
{
    vector<Record> book;
    int x;
    Record current;
public:
    void Menu()
    {
        int choice = 0;
        cout << "---Main Menu---\n";
        cout << "1. Input information\n";
        cout << "2. Display records\n";
        cout << "3. Exit\n";
        cin >> choice;
        switch (choice)
        {
            case 1:
                InputInfo();
                break;
            case 2:
                Display();
                break;
            case 3:
                Exit();
                break;
        }
    }
    void InputInfo()
    {
        string temp;
        cout << "How many records would you like to input?";
        cin >> x;
        while(x<10)
        {
            cout << "You must input at least 10 records. Please input a bigger value.\n";
            cin >> x;
        }
        for(int i = 0; i<x; i++)
            {
                cout << "What is the record number? ";
                cin >> temp;
                current.setRecNum(temp);
                cout << "What is the first name? ";
                cin >> temp;
                current.setFirstName(temp);
                cout << "What is the last name? ";
                cin >> temp;
                current.setLastName(temp);
                cout << "What is the age? ";
                cin >> temp;
                current.setAge(temp);
                cout << "What is the telephone number? ";
                cin >> temp;
                current.setTelephone(temp);
            }
        Menu();
    };
    void Display()
    {
        int i = 0;
        for(i=0; i<x; i++)
            {
                cout<<"Record number: ";
                cout<<current.getRecNum();
                cout<<"\n";
                cout<< "First name: ";
                cout<<current.getFirstName();
                cout<<"\n";
                cout<< "Last name: ";
                cout<<current.getLastName();
                cout<<"\n";
                cout<< "Age: ";
                cout<<current.getAge();
                cout<<"\n";
                cout<< "Telephone number: ";
                cout<<current.getTelephone();
                cout<<"\n";
                cout<<"\n";
            }
        Menu();
    };
    void Exit()
    {
        cout << "Closing...";
    };
} Recordsbook;

int main()
{
    Recordsbook.Menu();
}

[JLBorges]

Something like this, perhaps:

int get_choice()
{
    std::cout << "enter choice 1/2/3: " ;
    
    char choice ; 
    if( std::cin >> choice && choice > '0' && choice < '4' ) // valid choice: '1' '2' or '3'
        return choice - '0' ; // '2' - '0' == 2 etc.

    // invalid choice. try again
    std::cerr << "invalid choice. try again\n" ;
    return get_choice() ; // try again
}

And then:

    void Menu()
    {
        std::cout << "---Main Menu---\n";
        // etc

        const int choice = get_choice();

        switch (choice)
        {
            case 1:
                // etc 

[Griffinflame21]

I would just use an if statement, but I'm trying to work on exception catching. I couldn't find anything that helped me understand how to use it in this situation.

[JLBorges]

This is not a good use-case for using exceptions. However, this is how it could be used:

#include <iostream>

int get_choice()
{
    std::cout << "enter choice 1/2/3: " ;

    char choice ;
    if( std::cin >> choice )
    {
        if( choice > '0' && choice < '4' ) return choice - '0' ;

        else throw std::out_of_range( "invalid choice" ) ;
    }

    else throw std::runtime_error( "input failure on stdin" ) ;
}

int main()
{
    int choice = 0 ;

    while( choice == 0 ) // keep trying till we get a valid choice
    {
        try { choice = get_choice() ; }

        catch( const std::out_of_range& ) { std::cerr << "invalid choice. try again\n" ; }

        catch( const std::runtime_error& ) // input failure
        {
            std::cerr << "input failure on stdin. clearing the failed state. try again\n" ;
            std::cin.clear() ; // clear the failed state and try again
        }
    }

    std::cout << "choice is " << choice << '\n' ;
}