CODEWITHSUNDEEP
c++
LtMuffin
LtMuffin

Reputation: 219

Unable to check for non-integer input

The else statement in this code does not execute, instead, when a character is entered, it would get stuck in a continuous loop, repeating the lines 33 and 35.

I want to check if the user input is not an integer in the else statement and ask the user again to specify the age.

#include <iostream>
#include <windows.h>
using namespace std;

class User {
    string name;
public:
    string getName(){
        return name;
    }
    void setName(string newName) {
        name = newName;
    }
};

int main()
{
    /** Initialise Variables */
    string name;
    int age;
    User u1;
    bool running = true;


    while(running) {
    /** Welcome Message w/ User's Name */
    cout << "What is your name?: " << endl;
    cin >> name;
    u1.setName(name);
    cout << "Welcome, " << u1.getName() << "!" << endl;
    returnToAge:
    Sleep(1000);
    cout << u1.getName() << ", to continue, you have to be over 18." << endl;
    Sleep(1000);
    cout << "Please enter your age: " << endl;
    cin >> age;

        if (age >= 18) {
            cout << "You may continue..." << endl;
            Sleep(1000);
            //Enter rest of questionnaire here   


        }
        else if(age < 18) {
            cout << "You are underage! Please try again!" << endl;
            Sleep(1500);
            goto returnToAge;
        }
        else {
            cout << "INVALID INPUT!" << endl;
            goto returnToAge;
        }
    }

}

Upvotes: 1

Views: 92

Answers (3)

JeJo
JeJo

Reputation: 32852

Use std::cin::fail to check wether the user input is an integer.

Secondly, avoid maximum practice using gotos, as it produces Spaghetti code structure. You can replace the goto using a while loop as follows:

while (true) 
{
    // code
    std::cin >> age;
    if (!std::cin.fail() && age >= 18) // if cin not failed && the codition
    { 
        /* do something */
        break;   // break the loop!
    }
    else if (!std::cin.fail() && age < 18)  // if cin not failed && the codition
    {  
        /* do something  goto removeed */   
    }
    else { std::cout << "INVALID INPUT!" << std::endl; /* goto removeed */ }
}

Upvotes: 1

John Zwinck
John Zwinck

Reputation: 249153

You need to check if the input operation succeeded. The easiest way is:

if (cin >> age) {
    // now use age
} else {
    // error
}

Another way which is equivalent:

cin >> age;
if (!cin) {
    // error
}

Upvotes: 3

Henning Koehler
Henning Koehler

Reputation: 2637

The problem is that cin >> age will read an integer into age (as that's the only thing age can store), and no matter what integer that is (it's 0 for non-numbers), it will be either bigger or smaller than 18, hence why your else case is never reached.

To detect invalid input, you need to read in a string and then check whether that string represents a valid integer.

Upvotes: 2

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