How to use multiple files in C++

When I was a newcomer to the C++ scene, I personally, had a fair bit of trouble trying to figure out how to keep classes separate from the main.cpp file.

So I figured I would pass my knowledge around on here to help others who are starting to learn C++ - we will use a "Person" class as an example.

Technically, you could use a single file to hold the generic "Main" class and the "Person" class - but that would make re-usability difficult to organize and understand. So it is generally a good example to keep classes as finely grained as possible, and by that, I mean a single class per file.

To give you an idea of what it would look like when you have both classes in the same file, turn your attention to the code below:

int main(int argc, char** argv) {
    std::cout << "Hello World" << std::endl;
}

class Person
{
private:
    std::string m_givenname;
    std::string m_familyname;

public:
    Person() {};
    ~Person() {};

};

With the way our code is set up above, we can only access the class inside this one file. Not to mention Visual Studio will throw up a few errors when you attempt to use classes this way. It is inevitable that larger C++ applications will grow to be more than one file, so creating classes that can be expanded easily will be very useful later on when creating more complex software.

There are two files that need to be created (which are simple to create if using Visual Studio), those are a Header file which holds all of the predefined function prototypes - which is similar to an initial planning of the functions names and their arguments; and a CPP file which holds the guts of the functions themselves.

Using our "Person" class as an example again, I will show examples of the files below:

"Person.h" (Header file)

#include <iostream>

class Person
{
private:
    std::string m_givenname;
    std::string m_familyname;

public:
    Person();    //Constructor prototype
    ~Person();   //Destructor prototype
};

"Person.cpp" (CPP File)

#include "Person.h"

Person::Person()
{

}

Person::~Person()
{

}

Now, with this configuration for a class - all you need to do when you wish to use the class is to include a (class name may differ in your situation)

#include "Person.h"

Then just proceed to create an instance the way you usually would.

This prevents the class files from being loaded on every single file the software works with, which will save time and system resources, as you decide when and where to use it.