What's the proper way of calling C++ functions from other classes? - c++

Question

I'm currently working on a project that has several classes, and at times, I have to call functions from other classes to make things work. I want to know if the way I'm doing it is efficient, or if there is another way I should be doing this. Here's an example
class FirstClass{ // FirstClass.cpp
public:
void aFunction(){
std::cout << "Hello!";
}
private:
}
Let's say I wanted to call aFunction in another class, I'd do this:
#include "FirstClass.cpp"
class SecondClass{ //SecondClass.cpp
public:
FirstClass getFirstClass;
// I would then use getFirstClass.aFunction();
// whenever I want to call.
private:
}
I don't feel like this is very productive. Is there a better way of doing this?

Answer 1

First of all why including source file FirstClass.cpp?
The proper way is to create a header file FirstClass.h and a source file FirstClass.cpp and include the header inside the source and in main.cpp.
Second: A member function is a member function it is a member of an object so you need an instance of that class to call its member. If you don't want to instantiate the class then declare the member function as a static function then you can either call it using an object or directly using class name followed by scope operator: FirstClass::aFunction().
// FirstClass.h
class FirstClass{ // FirstClass.cpp
public:
void aFunction();
}
// FirstClass.cpp
#include "FirstClass.h"
void FirstClass::aFunction(){
std::cout << "Hello!";
}
// SecondClass.h
#include "FirstClass.h"
class SecondClass{
public:
void foo();
private:
FirstClass getFirstClass;
};
// SecondClass.cpp
void SecondClass::foo()
{
getFirstClass.aFunction();
}
To make it a static:
struct A
{
static void do_it(){std::cout << "A::do_it()\n";}
};
struct B
{
void call_it(){ A::do_it();}
};
There's nothing with "productivity" to whether have a static or non-static data/function member.
The semi-colon is not redundant at the end of class body so you need t add them: class FirstClass{ }; class SecondClass{};.