Writing function that returns two types

[laimaretto]

Hi all!

I have written a function that returns a string. It works as expected. It looks like this:

string myFunction (int i, string myString) {
  string output;
  if (everything==ok) {
      return output;
  } else {
      return "Error";
  }
}

Now, if the function fails, I'd rather like to send an integer. How should I do that? Is it possible?

I've read many posts where some people would suggest that I could pass an integer variable as reference and write that variable if the function fails or even pass a struct as reference and use it in such a way as well.

I just want to know what do you people think is the most appropriate (or elegant) way of doing it. Is there may be another way?

Thanks in advance!

BR,

Lucas

[Cubbi]

You could throw an exception (although it's best to throw something derived from std::exception rather than a plain integer)

[codewalker]

One way of doing it is pass the output type by reference, in this case a string, and return error code.
In case if no error return 0, in case or error return the error code.

[vince1027]

In addition to passing the return value as a reference type parameter, you can also return a struct type.

typedef struct Result
{
    int errorCode;
    string value;
}
Result;

Result myFunction()
{
    Result result;
    // some code here
    return (result);
}

Not really my preferred solution, but it's good to know alternatives.

[andywestken]

As a variation on vince1027's suggestion, you could return a pair (std::pair)

pair<string, int> myFunction (int i, string myString) {
  string output;
  if (everything==ok) {
      return make_pair(output, 0);
  } else {
      return make_pair("Error", 666);
  }
}

This trick is used by some STL functions, e.g. map::insert (the overload which inserts a value)

But I would go for either codewalker's reference solution or Cubbi's exception based one.

Note I would generally avoid the exception based solution in cases where the error was not rare/unexpected.

Andy