How to accept only numbers and strings in templates in C++11?

Question

As titlte says, in C++11, how can I declare a template that only accepts numbers (int, long, float and double) and strings?

template<typename T>
class CustomClass {
    public:
        T data;
};

Answer 1

Put this anywhere in the class definition:

static_assert(std::is_arithmetic<T>::value ||
              std::is_same<T, std::string>::value,
              "Wrong argument type");

Adjust condition to taste.