Construct a class that have default arguments with given arguments

Question

Example I have some random class, which constructor have some default arguments. And I have a function to construct there class with some given arguments, and I need somehow to check if I can construct there class with those given arguments

class someRandomClass
{
public:
    someRandomClass(int a = 0, float b = 0.f, double c = 0.0, const char* d = "") {}
    // any argument you can think of
};

template<typename Cls, typename... Ts>
void constructClass(Ts... args) {
    // something to check
    if (constructable(Cls, Ts...))
        Cls myClass(args...);
}

Are there some way to achieve this?

Does Function Pointer with default values answer your question? — Ted Lyngmo
– Ted Lyngmo, Commented Jun 14, 2022 at 5:52

Jarod42 · Accepted Answer · 2022-06-14 07:39:39Z

2

std::is_constructible traits might help (And you might get rid of fake_constructor :-) ):

template<typename Cls, typename... Ts>
// requires(std::is_constructible_v<Cls, Ts&&...>) // C++20,
                                                  // or SFINAE for previous version
void callClassConstructor(Ts&&... args)
{
    if constexpr (std::is_constructible_v<Cls, Ts&&...>)
    {
        Cls myClass(std::foward<Ts>(args)...);
        // ....
    }
}

answered Jun 14, 2022 at 7:39

Jarod42

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