Create std::array from variadic template

问题

I'd like to achieve something like that:

#include <string>
#include <array>

enum class MyEnum{
  A,
  B,
  C
};

template<MyEnum... Args>   
class MyClass{
  public:
    MyClass()
    {
    }
  private:
    std::array<MyEnum, sizeof...(Args)> array;   
};

Now I have an array, which can hold all passed to template values. But how can I populate this array with template parameters?

回答1:

If what you are wanting is to put all the MyEnum values into array, then you can unpack them into an initialiser list and initialise array with it initialise it with direct initialisation:

MyClass() : array {{ Args... }} { }

You need a fairly new compiler to use this syntax, however.

Thanks to Xeo for correcting my answer.

回答2:

MyClass()
{
    std::initializer_list<MyEnum> il( {Args...} );
    std::copy (il.begin(), il.end(), array.begin());
}

来源：https://stackoverflow.com/questions/10364874/create-stdarray-from-variadic-template