How to call void from a different class?

[reversel]

GUI.cc

  SomeClass::Dothing(); //A nonstatic member reference must be relative to a specific object 

SomeClass.cpp

  class SomeClass
{
  public:
  void Dothing(); //This is what I want to use.

}

[Ganado]

First, minor terminology critique: You don't call 'void', you call a function (which happens to have a return type of void).

If a class member function is not static, you need an instance of that class (an object), for the function be called on.

int main()
{
    SomeClass somebody;
    somebody.Dothing();
}

Otherwise, make the function static.

class SomeClass
{
  public:
  static void Dothing();
};