CODEWITHSUNDEEP
c++
imessedup
imessedup

Reputation: 25

C++ How to make a non void function return nothing for if else statements?

So my problem goes like this:

string something (string something){
    string letter;
    cout << "press a";
    cin >> letter;
    if (letter==a){
        return a;
    }
    else
    cout << "wrong letter";
    //what should I put here if I don't want it to return any value?
}

Any alternatives would also be welcome

Upvotes: 0

Views: 390

Answers (3)

Skam
Skam

Reputation: 7798

One way to handle this would be a std::optional<std::string>

#include <optional>

std::optional<std::string> dingas(std::string something)
{
    string letter;
    cout << "press a";
    cin >> letter;
    if (letter==something){
        return "a";
    }
    else
    {
        std::cout << "wrong letter";
        return std::nullopt;
    }
}

[1] https://en.cppreference.com/w/cpp/utility/optional

Upvotes: 3

Bathsheba
Bathsheba

Reputation: 234695

Consider using the exception mechanism for this: this carries the advantage that you can keep a reasonable return type, and you can also delegate handling of the exception to the caller of the function.

First, write

struct WrongLetterException : public std::exception{};

Then change the function to

std::string something (std::string something/*ToDo - is this correct?*/){
    std::string letter;
    std::cout << "press a";
    std::cin >> letter;
    if (letter == "a"/*note the change here*/){
        return a;
    }
    throw WrongLetterException();
}

In the caller to the function, you then catch (const WrongLetterException& ex) and deal with it as you see fit.

Upvotes: 2

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122341

If you want to read a single character you could use a char. However, if the function is declared to return a std::string but you do not want to return a std::string you have several options:

  • return an empty std::string
  • change signature to bool something(std::string& out) such that the return value signals sucess and when it is true the result is written to out.
  • change the return type to std::optional<std::string>. A std::optional<std::string> either contains a std::string or not.
  • throw an exception instead of return

Which one you pick is up to you. Exceptions should be used for exceptional cases, so you need to decide if not returning is "normal" or exceptional. It will require the caller to handle the exception. bool something(std::string&) is similarly inconvenient for the caller, because they need to check the return value and provide the string to be used. Usually a sentinal value (ie giving special meaning to the empty string) can cause problems, because one day you might confuse the sentinal with a proper return value. Though, as the function either returns a string with a single character or not, this isnt a big issue. I'd prefer the std::optional, but thats just my biased opinion.

Upvotes: 2

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