How to check what constructor overload is used

November 28, 2024

If I have a class constructor with two overloads taking in different inputs, is there a way to tell them apart? For example,

class example
{
    double ExampleDouble;
    char ExampleChar;
    public:
    example(double ED)
    {
        ExampleDouble=ED;
    }
    example(char EC)
    {
        ExampleChar=EC;
    }
};
int main()
{
    example var('a');
    return 0;
}

Is there any way to tell whether "var" is storing a double or char?

I tried using var.ExampleChar but it threw an error, and there were no online resources regarding this issue.

>Solution :

The simple way would be to do something like this

class example
{
public:
    double ExampleDouble;
    char ExampleChar;
    bool IsChar;
    example(double ED)
    {
        ExampleDouble=ED;
        IsChar=false;
    }
    example(char EC)
    {
        ExampleChar=EC;
        IsChar=true;
    }
};

But you are reinventing the wheel. The class you have here is similar to what std::variant already does for you.

#include <variant>
#include <iostream>

int main()
{
    std::variant<double, char> var('a');
    if (holds_alternative<char>(var))
        std::cout << "its a char\n";
    return 0;
}