Question

Here is my simplified data structure:

Object1.h

template <class T>
class Object1
{
  private:
     T a1;
     T a2;
  public:
     T getA1() {return a1;}
};

Object2.h

template <class T>
class Object2: public Object1 <T>
{
   private:
      T b1;
      T b2;
  public:
     T getB1() {return b1;}
}

Is there any way to get the type T from an object in the following function:

Functions.h

template <class Object>
void (Object *o1, Object *o2)
{
   T = o1->getA1();  // Is it possible to get T from object o1?
   // ...
}

Or must we give additional information about data types of both objects, like this:

template <class T, class Object>
void (Object *o1, Object *o2)
{
   T = o1->getA1();
   // ...
}

Answer 1

Add a using or typedef statement, like this:

template <class T>
class Object1
{
private:
    T a1;
    T a2;
public:
    T getA1() const {return a1;}

    using type = T;
    // or
    typedef T type;
};

template <class Object>
void foo(Object *o1, Object *o2)
{
    typename Object::type x = o1->getA1();
    // ...
}