Where to place variables of a function in multifile compilation

Question

I have an application that has classes and functions all within the source file. I've been reading on how to place them into dedicated .cpp & .h files. However, I've noticed that the .h file will only include the definitions and the .cpp file only contains the implementation of the functions and not the data members.

My question is if I want to have classes in separate files, which of the two would the variables of a function be defined in?

Here is some code information:

Class:

    class Post {    //Will hold the contents of a single post.

private:
    int UserID;
    std::string message;
    //time_t date; // Will eventually hold a time value.
public:

    static void postMenu(User& currentUser, bool loggedIn) {
        std::cout << "\n**********************************\n          POST MENU\n**********************************\n\n";

        char postChoice = ' ';
        std::cout << "\n[P] - Post to board.\n[V] - View Board.\n[E] - Exit to main menu.\n\n>";
        std::cin >> postChoice;
        postChoice = toupper(postChoice);

        if (postChoice == 'P') {
            Post currentUserPost;//Initilize current post.
            currentUserPost.loadPosts();
            currentUserPost.postMessage(currentUser, loggedIn);
            currentUserPost.loadPosts();
            //PlaySound(TEXT("C:/Users/19097/Desktop/Programs/Registration Application/App files/Audio/ding.wav"), NULL, SND_FILENAME | SND_ASYNC); // Sound when message is posted
        }
        else if (postChoice == 'V') {
            Post::loadPosts(); //Loads the post wall for viewing
        }
        else if (postChoice == 'E') {
            std::cout << "\nExiting..." << std::endl;
            return;
        }
    }
    char postMessage(User& currentUser, bool loggedIn) {    //Will post a message to the board. Passes a User object.
        if (loggedIn == false) {
            std::cout << "You must be logged in to post!" << std::endl;
            User::userLoginRegisterPrompt();
            return 'F';
        }

        std::string message; //Actual message string

        std::cout << "\nEnter your message: ";
        std::cin.ignore(); //Clears string buffer.
        getline(std::cin, message);
        std::ofstream post("App files/UserPosts/-Posts.txt", std::ios::app); //File with user posts.
        post << currentUser.getUserName() << ": " << message << std::endl;
        post.close();
        logAction(currentUser.getUserName(), "Made a post");
    }
    static bool loadPosts() {   //Will be for viewing the post history.
        std::ifstream post("App files/UserPosts/-Posts.txt");
        std::string line;

        if (!post) {
            std::cout << "No board exists!" << std::endl;
            return false;
        }
        std::cout << "\n**********************************\n          GLOBAL POST\n**********************************\n\n";
        while (getline(post, line)) {
            std::cout << line << std::endl;
        }
        std::cout << "\n\n**********************************\n**********************************\n\n";
    }

};

How would the .cpp and .h files for this class look? I saw an example where the declarations were declared within the .h file and all the function bodies were left in the .cpp file.

However, they stated that all data members and class/static keywords should be removed from .cpp file.

This is the tutorial for reference: https://www.youtube.com/watch?v=nbd7o8iKh9Q&ab_channel=CalebCurry

Can you be more precise and provide us some code example on which you're trying to apply this header and source file approach. So that we can modify that example and tell you exactly how to do what you need. — Jason, Jan 24 '22 at 04:35

score 0 · Answer 1 · answered Jan 26 '22 at 04:29

How would the .cpp and .h files for this class look?

You can use this as a reference.

post.h

#ifndef POST_H //ALWAYS USE INCLUDE GUARDS IN HEADER FILES
#define POST_H
#include <string>
class Post {    

private:
    int UserID;
    std::string message;
    
public:
 
    //declarations for member functions
    static void postMenu(User& currentUser,bool loggedIn); 
    char postMessage(User& currentUser,bool loggedIn);
    static bool loadPosts();

};
#endif

post.cpp

#include "post.h"
#include <fstream>
#include <iostream>
//dont forget to include the header that has User class

//this is implementation of the static member function postMenu
void Post::postMenu(User& currentUser, bool loggedIn) {
      //add code here  
}

//this is implementation of the non static member function postMessage
char Post::postMessage(User& currentUser, bool loggedIn) {    //Will post a message to the board. Passes a User object.
        
        //add code here
        
        return 'Q';
}

//this is implementation of the static member function loadPosts
bool Post::loadPosts() {   
        
        //add code here
        
        return true;
}

Modifications

Some of the modifications that i made include:

Added include guards in the header post.h. This is a recommended practice.
In the header file post.h, we have only declarations for the member functions.
In the source file post.cpp, we have the definitions corresponding to each of the member function.

Also, i would recommend you to learn using books listed here instead of youtube videos.

Where to place variables of a function in multifile compilation

1 Answers1

Modifications