CODEWITHSUNDEEP
c++
lephe
lephe

Reputation: 327

Undefined argument list

I have a C++ template class (in Qt) that should handle a list of custom items. This class has a simple member function that is supposed to call the constructor of the template type and add the created item to the list.

void CustomList::addElement(void)
{
    T *element = new T();
    // ...
}

But I have a problem : I'd like this function to be able to call overloaded constructors.

I thought I could give it the arguments that should be used in the constructor. So it would be called with as arguments a "copy" of the arguments given to addElement().

Except that I don't know how many of them there are, no more than their types. Any simple way I could do it ?

Upvotes: 2

Views: 158

Answers (1)

Columbo
Columbo

Reputation: 60979

So it would be called with as arguments a "copy" of the arguments given to addElement().

Why copies when you can use the original arguments?

With C++11 you can use variadic templates and perfect forwarding:

template <typename... Args>
void CustomList::addElement(Args&&... args)
{
    T *element = new T(std::forward<Args>(args)...);
    // ...
}

Without proper C++11 support you will have to overload the addElement function (template) for every amount of arguments until a sensible limit is reached. I.e.

template <typename Arg1>
void CustomList::addElement(Arg1 const& arg1)
{
    T *element = new T(arg1);
    // ...
}

template <typename Arg1, typename Arg2>
void CustomList::addElement(Arg1 const& arg1, Arg2 const& arg2)
{
    T *element = new T(arg1, arg2);
    // ...
}

// [...]

Upvotes: 5

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