c++ string validation for user input

Question

All I want to do, is prompt a user for a yes or no answer, and validate this to ensure they haven't typed something stupid.

I thought this would be a relatively straight forward task, however after many failed attempts at it myself, and looking around online, it seems everyone has a different opinion on the best way to do it.

Pseudocode

Ask question
prompt user
check if input = yes or input = no
if yes, do scenario a
in no, do scenario b
if invalid, return to point 2

Code

main.cpp

std::cout << "Do you have a user name? ("yes", "no"): ";
std::cin >> choice;
user.validation(choice);

if (choice == "yes")
{
// some code
}

if (choice == "no")
{
// some code
}

User.cpp

void User::validation(std::string choice)
{
    while (choice != "yes" && choice != "no")
    {       
        std::cout << "Error: Please enter 'yes' or 'no': ";
        std::cin >> choice;
        if (choice == "yes" && choice == "no")
        {
            break;
        }

    }
}

This works, up until they eventually type yes or no, when it jumps past if yes, and if no, straight onto the next part of the program

And I want to be able to call user.validation multiple times throughout the program to validate other yes/no questions

"I want to be able to call user.validation multiple times", what prevents you do it? — MeNa
– MeNa, Commented Dec 10, 2013 at 17:50

Duncan Smith · Accepted Answer · 2013-12-10 17:51:49Z

3

Try changing this

if (choice == "yes" && choice == "no")

For this

if (choice == "yes" || choice == "no")

Choice cannot be "yes" and "no" at the same time.

answered Dec 10, 2013 at 17:51

Duncan Smith

5382 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

MeNa Over a year ago

This is not an answer to the question!

user3001499 Over a year ago

Also changed this thanks, I thought it should be || not &&. but before I changed it to &choice as shown by @PhillipKinkade, || did not work at all for some reason

Phillip Kinkade · Accepted Answer · 2013-12-10 17:48:51Z

2

You are not returning the corrected choice from validation():

void User::validation(std::string &choice) // <-- insert a & here

answered Dec 10, 2013 at 17:48

Phillip Kinkade

1,43213 silver badges18 bronze badges

3 Comments

user3001499 Over a year ago

Thanks @Phillip Kinkade so this appears, on the surface at least, to have fixed my problem, but what is better practice, to use std::string compare() or to pass by reference (which is what I think you have shown above).

Phillip Kinkade Over a year ago

I prefer using == over std::string::compare(). Pass by reference is used a lot in C++. It depends on the situation if it's better or not.

user3001499 Over a year ago

thanks, will definitely do some research and reading up in this area

S Farron · Accepted Answer · 2013-12-10 17:43:36Z

-1

C/C++ doesn't work like this for strings as the == operator isn't doing what you think it's doing for std::string objects and char* arrays. Use the std::string compare() method instead. Reference: http://www.cplusplus.com/reference/string/string/compare/

answered Dec 10, 2013 at 17:43

S Farron

5711 gold badge5 silver badges10 bronze badges

Collectives™ on Stack Overflow

c++ string validation for user input

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related