Is there a function to call the class name in a template<> without typing the name of the class yourself?

Question

I am trying to get the type name of a class. Of course, I could just use typename(class) but I need to place it in a template like this

ClassA<typeid(class).name()> a = ClassA<typeid(class).name()>(args);

This is what I tried:

template<class T>
class A
{
public:
   T t; // the class

   A(T t1)
   {
      t = t1;
   }
};

class B // example class
{
public:
   int i;

   B(int i1)
   {
      i = i1;
   }
};

int main()
{
   B b = B(1);
   A<typeid(b).name()>(b) a = A<typeid(b).name()>(b); // my issue
}

But it always gives me an error.

'A': invalid template argument for 'T', type expected.

Is there any way round this (class A needs to be able to accept any class in one attribute)?

Answer 1

Is there any way around this (class A needs to be able to accept any class in one attribute)?

What you are looking for is the decltype keyword. You need

A<decltype(b)> a = A<decltype(b)>{ b };
// or just
auto a = A<decltype(b)>{ b };

However, since c++17, thanks to CTAD, which allows you to write just.

A a{ b }; // no need of "A<-template-para-list->"

---

Side note: If you do not initialize the members in the constructor initializer list, the passed T in A must be default constructible. Therefore, I would recommend

template<class T>
class A
{
    T t;
public:   

    A(T t1)
        : t{ t1 } // ---> initialize in constructor initializer list
    {}
};

Live demo in godbolt.org