非类型模板数组？

Question

I have a non-type template class Foo:

template <int n>
class Foo {
public:
  Foo(){}
};

How can I store multiple instances of that class in one array? (When the instances all have different template values.)

This, however, does not work:

Foo<int> myArray[] = {Foo<1>() , Foo<2>() , Foo<3>()};

Compiler error is: template argument for non-type template parameter must be an expression

Answer 1

Foo<1> is not the same type as Foo<2> (and so on), so you can't store them in a array (if they derived from FooBase , you may have an array of FooBase* ).

You may store them in a std::tuple :

auto foos = std::make_tuple(Foo<1>() , Foo<2>() , Foo<3>());

Answer 2

template <int n>
class Foo : public Ifoo {
public:
  Foo(){}
};

IFoo* myArray[] = {..

Answer 3

As had been mentioned, Foo<1> is a different type to Foo<2> etc etc, so you can't store them in an array.

To get around this you can de-template the class and make the integer a constructor argument instead:

class Foo {
public:
  Foo(int n){}
};

Foo myArray[] = {Foo(1) , Foo(2) , Foo(3)};