Verify user input is 5 digit number

Question

I am working on a project where the user is prompted to enter a zip code. I need to verify it is a five digit number (I don't need to verify it is an actual zip code).

Here is a portion of my code.

string userInput;
cout << "Zip Code> ";
getline(cin, userInput, '\n');


while (stoi(userInput)<10000 || stoi(userInput) > 99999){
    cout << endl << endl << "You must enter a valid zip code. Please try again." << endl;
    cout << "Zip Code>" << endl;
    getline(cin, userInput, '\n');
}

PropertyRec.setZipCode(stoi(userInput));

This works fine unless the zip code starts with a zero. If it does, the validation is no good and the initial zero never saves to the variable once the input string is converted to an integer.

Should I leave the zip code as a string when saving to the database? If so, how can I verify there are exactly 5 characters and each character is numeric?

Just check that there are five characters in the input and that each character is a digit. — Pete Becker, Apr 20 '16 at 00:15
Also, don't use `std::endl` unless you need the extra stuff that it does. `'\n'` ends a line. — Pete Becker, Apr 20 '16 at 00:15
the above comments are better than doing this, but for future reference, you could `int code = stoi(userInput)` and then use `code` rather than recomputing `stoi(userInput)`. If you can do something once and cache the result, you usually come out ahead. — user4581301, Apr 20 '16 at 00:19

PaulMcKenzie · Accepted Answer · 2016-04-20T00:45:13.557

9

Use std::all_of, isdigit and string::size() to determine if the zip code is valid:

#include <string>
#include <algorithm>
#include <cctype>
//...
bool isValidZipCode(const std::string& s)
{
   return s.size() == 5 && std::all_of(s.begin(), s.end(), ::isdigit);
}

Live Example

Declarative Programming plug:

Note that if you say out loud the line in the isValidZipCode function, it fits your description (the string must have a size equal to 5 and "all of" the characters must be a digit).

edited Apr 20 '16 at 00:45

answered Apr 20 '16 at 00:34

PaulMcKenzie

34,698
4
24
45

Thanks guys! Works great. – Brent Apr 20 '16 at 00:49

score 4 · Answer 2 · edited May 23 '17 at 11:45

Since you are receiving input as a std::string, you can use std::string::length (or std::string::size) to ensure you have the right amount of characters:

if (userInput.length() != 5)
{
    // Input is invalid
}

To ensure they're only numbers, as @user4581301 points out you can use std::all_of and isdigit (or check out answers in this question)

if (userInput.length() == 5 && std::all_of(s.begin(), s.end(), ::isdigit))
{
    // Input is valid
}

It's also worth noting that the following line

PropertyRec.setZipCode(stoi(userInput));

Will remove any leading 0 you have, so you may need to store your zip code as a std::string (unless you implement handling that will assume any zip code that's < 5 has leading 0's, but it's likely far easier to store it exactly as-is)

score 0 · Answer 3 · answered Apr 20 '16 at 01:58

0

You can use string size function for getting the size of the string. Save the string size in other variable and validate it whether it less than five or not.

answered Apr 20 '16 at 01:58

prince thomas

1

Verify user input is 5 digit number

3 Answers3