Question

I have two basic questions. The first one is about function in other classes. If I have a header file with a class in it and I want to use that function in another class I have created, do I always have to construct a class object to run a function in that class like:

someclass class; <----object construction
class.somefunction();  

Is there a way just to call the function with the object construction?

And the second question is it okay to put multiple small classes in one header file?

Answer 1

Functions should only be member functions if they act on an object of the class. Functions that don’t act on an object should just be plain global functions (or class static):

// Global function
void foo() { /* do something */ } 

// Static function
class Foo
{
public:
  static void foo() { /* do something */ }
};

For your second question, yes it’s ok. Generally people stick to one class per file, but in my opinion there’s nothing wrong with having a few small classes in a single file.