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();
}

[kbw]

You will, in effect, end up with:

try
{
    cin >> choice;
    if (! (1 <= choice && choice <= 3) )
        throw std::out_of_range("choice out of range");
}
catch (const out_of_range &)
{
    cerr << "An error occurred. Please choose a valid menu item number.";
}

Now, that can be encapsulated in a function or a type, but that's the code that needs to be run to get that result.

You should catch by reference at least, and const reference if you can.

[keskiverto]

Please do not doublepost. The other thread: http://www.cplusplus.com/forum/general/219131/

[boost lexical cast]

Also, you will need to include the <stdexcept> library for std::out_of_range.

kbw wrote:

Now, that can be encapsulated in a function or a type, but that's the code that needs to be run to get that result.

To the OP: You can have a friend function (or just a function) which overloads the >> operator (std::cin >> type) that throws an error when the input is invalid.

std::istream& operator>>(std::istream& is, const class_type& rhs)
{
    // take input with is and throw error if input is invalid
    // this function should be called within a try block and of course catch blocks should follow it
    // or you could just ask the user to re-enter input in here
    return is; // return std::cin at the end
}