Question

Hey im trying to validate a string. Basically what i want it to do is prevent the user from entering anything other than a string. Here is my code:

**getString**

string getString(string str)
{
    string input;
    do
    {
        cout << str.c_str() << endl;
        cin >> input;
    }
    while(!isalpha(input));
    return input;
}

Errors

Error   2   error LNK2019: unresolved external symbol "public: bool __thiscall Validator::getString(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?getString@Validator@@QAE_NV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function "public: void __thiscall Player::information(void)" (?information@Player@@QAEXXZ)    C:\Users\Conor\Documents\College\DKIT - Year 2 - Repeat\DKIT - Year 2 - Semester 1 - Repeat\Games Programming\MaroonedCA2\MaroonedCA2\Player.obj    MaroonedCA2
Error   3   error LNK1120: 1 unresolved externals   C:\Users\Conor\Documents\College\DKIT - Year 2 - Repeat\DKIT - Year 2 - Semester 1 - Repeat\Games Programming\MaroonedCA2\Debug\MaroonedCA2.exe MaroonedCA2
    4   IntelliSense: no suitable conversion function from "std::string" to "int" exists    c:\Users\Conor\Documents\College\DKIT - Year 2 - Repeat\DKIT - Year 2 - Semester 1 - Repeat\Games Programming\MaroonedCA2\MaroonedCA2\Validator.cpp 72  17  MaroonedCA2

Main

cout << "What is your name ?\n";
    name = validator.getString();<------This skips.

    cout << "\nWhat is your age? ";
    age = validator.getNum();

    string character = "What is your sex M/F?";
    sex = validator.getChar(character);


    cout <<"Name:\n"<< name<<" Age:\n" << age<< " Sex:\n"<< sex <<"\n";

New getString function.

string Validator :: getString()
{
   string input;
    do 
    {
    } 
    while (
    std::find_if_not( 
        std::begin(input), //from beginning
        std::end(input), //to end
        isalpha //check for non-alpha characters
    ) != std::end(input) //continue if non-alpha character is found
);
    return input;
}

Answer 1

The first problem described is that this function belongs to a class, but you forgot to specify that:

string Validator::getString(string str)
       ^^^^^^^^^^^

Next, isalpha takes an int (due to C reasons), and, as far as I know, there is no version for std::string. You can, however, use standard algorithms to do this:

do {
    ...
} while (
    std::find_if_not( 
        std::begin(input), //from beginning
        std::end(input), //to end
        isalpha //check for non-alpha characters
    ) != std::end(input) //continue if non-alpha character is found
);

This find_if_not call will search through the string and check if any non-alpha characters are found by comparing the return value to the ending iterator of the string. If they’re equal, the string is clean. You might also have to cast isalpha because it expects a predicate taking a char, not an int.

For some samples using this algorithm, see here. Note that due to the version of GCC on there, std::begin() and std::end() were replaced, and the != was changed to == due to the reversed logic of the function (you’d use it like do {} while (!ok(...));).