Template and function pointer - c++

Question

Is it somehow possible to store the class from a template without making the the whole class a template?
Task:
I have two functions, v1 without parameters and v2 with parameters,
If v1 was called somewhere nothing happens with Use(), if v2 was called somewhere Use() should execute a function_ptr with the instance I got from DoSometh(T*).
e.g.
class MyClass
{
//v1 no parameters
void DoSomething()
{
}
//v2 with parameter
template<class T>
void DoSomething(T* instance, void (T::*func)())
{
store somewhere?? = instance;
}
void Use()
{
//if DoSometh(T* instance) was used before
if(instance != NULL)
{
(*instance->)//call function pointer from DoSomething(T*,void (T::*)())
}
}
}
std::function problem
update:
class Timer : public ITickable
{
std::function<void()> test; //adding this does weird things
virtual void Tick() {}
}
class MyClass
{
ITickable* tickable_;
void Tick()
{
tickable_->Tick(); //let's assume it points to a Timer obj.
}
}

Answer 1

I think std::function and std::bind (C++11) do accomplish what you want, as already suggested in the comments. A simplified mock-up of your Timer class could be:
class Timer
{
std::function<void()> m_task;
public:
template <typename T>
void setTask(T &instance, void (T::*fcn)()) // consider T const & if applicable
{
m_task = std::bind(fcn, &instance);
}
void fire()
{
if (m_task) // std::function overloads operator bool()
m_task();
}
};
When setTask is called with an object and a member-function that can be called on this object, a std::function object is created (you could choose to do this in a constructor of course). When the timer fires, this object is checked (using operator bool(), provided by std::function), and if it is callable (e.g. when setTask() has been called before), it calls the function.
For example:
class MyClass
{
public:
void func()
{
std::cout << "Hi from MyClass\n";
}
};
class MyOtherClass
{
public:
void func()
{
std::cout << "Hi from MyOtherClass\n";
}
};
int main(int argc, char **argv)
{
MyClass x1;
MyOtherClass x2;
Timer t1, t2;
t1.setTask(x1, &MyClass::func);
t2.setTask(x2, &MyOtherClass::func);
t1.fire();
t2.fire();
}