Unable to get appropriate Input validation for Integer

Question

double age = 0;
int empAge;

cout << "Please enter your age in integers: ";
cin >> age;

// Input validation for age. To prevent input with a decimal number eg 5.6, 7.8, 90.9, etc

while(cin.fail() || ((int)age != (double)age)){
    cout << "\nThat is not a valid option, please try again. ";
    cin >> age; 

    if(cin.fail() || (int)age != double(age)){
        cin.clear();
        string not_an_int;
        cin >> not_an_int;
    }
    cout << "That is not a valid option, please try again. ";
    cin >> age;
}
// Assigns the data in variable of double type age to the variable of int type empAge   
age = empAge;

What I need to get done ? Ask user to enter a integer digit only. If not an integer give error "That is not a valid option, please try again" and ask user to enter again.

Attached is also an image showing errors my code gives with the inputs used.

You probably want to call cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); right after cin.clear() instead of string not_an_int etc. — n. m. could be an AI
– n. m. could be an AI, Commented Aug 25, 2018 at 10:05
"Attached is also an image showing errors my code gives with the inputs used." Don't post images of text. Copy-paste text into the question, as text. — Algirdas Preidžius
– Algirdas Preidžius, Commented Aug 25, 2018 at 10:18
I don't understand what the question is. Please clarify your question. What is the problem? — Coral Kashri
– Coral Kashri, Commented Aug 25, 2018 at 12:08
Reading the comments in your code, I think you are supposed to do something like int tmp_age; cin >> tmp_age; ... // check for input fails ... double age = tmp_age;, which would make the last assignment (or comment) to have sense. — Bob__
– Bob__, Commented Aug 25, 2018 at 14:19
@KorelK Apologies for the ambiguity. Basically i need the user to input a integer value, if it is not an integer then give error. Keep repeating until user enters an integer value. Just trying to remove bad input such as alphabets, decimal numbers. — Hirnesh
– Hirnesh, Commented Aug 25, 2018 at 17:22

Geezer · Accepted Answer · 2018-08-25 19:00:18Z

What I need to get done ? Ask user to enter a integer digit only. If not an integer give error "That is not a valid option, please try again" and ask user to enter again.

I advise you to read this carefully, as it is quite unclear what exactly you are asking.

I've prepared this small snippet for you in case you are asking something like How do I read user input using stdin while validating it is only an integer value?

#include <iostream>
#include <string>
#include <limits>

bool is_natural(const std::string s)
{
    return s.find_first_not_of( "0123456789" ) == std::string::npos;
}

int main()
{
    std::string input;
    while (!(std::cin >> input) || !is_natural(input))
    {
        std::cout << "That is not a valid option, please try again.\n";
        std::cin.clear();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    }

    int age = std::stoi(input);
    std::cout << "Age (natural integer value) entered: " << age << "\n";
}

coccodio · Accepted Answer · 2018-08-25 15:44:06Z

If you want to read only integers in input, this is a possible solution:

#include <iostream>
#include <string>

using namespace std;

int main() {
    int age;
    unsigned long status;
    string myString;
    do {
        cout << "Please enter your age in integers: ";
        getline(cin, myString);

        /*
         * Return the position of the first character that does not match.
         * Else return "string::npos"
         */
        status = myString.find_first_not_of("0123456789");

        if (status != string::npos)
            cout << "That is not a valid option, please try again." << endl;
    } while (status != string::npos);

    //Convert string to int.
    age = stoi(myString);

    cout << "Age as integer: " << age << endl;
}

You can use stoi() only in c++ 11 or following:

int num = stoi( str )

Old method:

int num = atoi( str.c_str() )

Coral Kashri · Accepted Answer · 2018-08-25 23:30:03Z

0

using namespace std;

// The method check if the string only contains digits
bool is_digits(const std::string &str)
{
    return std::all_of(str.begin(), str.end(), ::isdigit);
}

int main()
{
    int age;
    bool status = false;
    string myString;
    while (!status) {
        cout << "Please enter your age in integers: ";
        cin >> myString;

        status = is_digits(myString);
        if (!status)
            cout << "That is not a valid option, please try again." << endl;
    }

    //Convert string to int.
    age = stoi(myString);

    cout << "Age as integer: " << age << endl;
    return 0;
}

answered Aug 25, 2018 at 23:30

Coral Kashri

3,5162 gold badges12 silver badges24 bronze badges

Collectives™ on Stack Overflow

Unable to get appropriate Input validation for Integer

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related