Question

I have a function that currently takes in two template parameters. One is expected to be the smart pointer, and the other is expected to be the object type. For example, SmartPtr<MyObject> as the first template parameter and MyObject as the second template parameter.

template <typename T, typename TObject>

I would like to know whether I can determine the second parameter, MyObject, automatically from the first parameter SmartPtr<MyObject> or not so that my template function is written like this:

template <typename T>

And the type TObject in the original template function is automatically determined from T which is expected to be a smart pointer.

As requested, here is the function declaration and its use:

template <typename T, typename TObject>
T* CreateOrModifyDoc(T* doc, MyHashTable& table)
{
    T* ptr = NULL;

    if (!table.FindElement(doc->id, ptr))
    {
        table.AddElement(doc->id, new TObject());
        table.FindElement(doc->id, ptr);
    }       

    return ptr;
}

Answer 1

If you know that the first template parameter will be the smart pointer type, why not declare your function with only one parameter and use it as such:

template<typename T>
void WhatIsIt(SmartPtr<T> ptr)
{ 
    printf("It is a: %s" typeid(T).name());
}