Using multiple classes and linked lists - c++

Question

Currently I'm trying to use multiple classes (each with their own .cpp and header .h file) and link them using a main .cpp. I want to make a temporary new video object pointer, pass in the arguments, insert it into the linked list, and delete the temporary pointer. Afterwards, I need to print each individual node of the list.
Currently there are 4 files: main.cpp, vlist.cpp, vlist.h, video.cpp, and video.h
I am using vlist as a way to construct a linked list which gets passed in a video object pointer with the insert function defined in the vlist.cpp file.
The first problem being that I'm not sure I am doing that correctly. At the moment, all I'm doing to be able to pass a video object in another class is by including video.h in the vlist.h file.
The second problem is that I cannot figure out how to properly access the individual video object attributes in each node because my getter functions (defined in video.h) won't work. They seem to return an address rather than a value. However, whenever I try to fix that, it tells me that I cannot use the getter function like this.
My third and final problem is that in vlist.cpp I cannot pass in m_vid when creating a new node but I can pass in m_head just fine. It won't compile if I don't use myVid (a publicly declared video object pointer in vlist.h).
Files below:
main.cpp
#include <iostream>
using namespace std;
#include "vlist.h"
#include "video.h"
int main()
{
//Create temporary video object pointer using Video * temp = new Video(arguments);
//Pass in the temp video pointer to the list and insert it with VList function
string firstLine, secondLine, thirdLine = "";
float fourthLine = 1.1;
int fifthLine = 2;
VList list;
Video * tempVid = new Video(firstLine, secondLine, thirdLine, fourthLine, fifthLine);
list.insert(tempVid);
delete tempVid;
list.print();
return 0;
}
video.cpp
#include "video.h"
#include <iostream>
using namespace std;
Video::Video(string title, string URL, string comment, float length, int rating) {
vidTitle = title;
vidURL = URL;
vidComment = comment;
vidLength = length;
vidRating = rating;
}
void Video::print(Video *myVid) {
cout << myVid->getTitle() << endl;
}
video.h
#ifndef VIDEO_H
#define VIDEO_H
#include <string>
#include <iostream>
using namespace std;
class Video
{
public:
Video(string title, string URL, string comment, float length, int rating);
int getRating() {
return vidRating;
}
float getLength() {
return vidLength;
}
string getTitle() {
return vidTitle;
}
string getURL() {
return vidURL;
}
string getComment() {
return vidComment;
}
void print(Video *myVid);
private:
string vidTitle, vidURL, vidComment, vidPreference;
float vidLength;
int vidRating;
};
#endif
vlist.cpp
#include <iostream>
using namespace std;
#include "vlist.h"
VList::VList() {
m_head = NULL;
}
VList::~VList() {
Node *ptr = m_head;
while (ptr != NULL) {
Node *temp;
temp = ptr;
ptr = ptr->m_next;
delete temp;
}
}
void VList::insert(Video *myVid) {
m_head = new Node(myVid, m_head);
}
void VList::print() {
Node *ptr = m_head;
while (ptr != NULL) {
cout << ptr->m_vid->getTitle();
ptr = ptr->m_next;
}
}
vlist.h
#ifndef VLIST_H
#define VLIST_H
#include "video.h"
class VList
{
public:
VList();
~VList();
void insert(Video *myVid);
void print();
Video *myVid;
private:
class Node
{
public:
Node(Video *myVid, Node *next) {
m_vid = myVid;
m_next = next;
}
Video *m_vid;
Node *m_next;
};
Node *m_head;
};
#endif

Answer 1

The first problem being that I'm not sure I am doing that correctly.
At the moment, all I'm doing to be able to pass a video object in
another class is by including video.h in the vlist.h file.
No, you are not doing it correctly, In the file main.cpp you are creating a pointer to Video(i.e, a Video*) and passing it to void VList::insert(Video *myVid) function and at the next line you are deleting the pointer before printing it. Remember that, when you create pointers and pass it to a method its lifecycle is not managed automatically like a magic, you yourself need to manage the pointers (which is the most common issue beginners face, I too). So there are two fixes to this problem
First Fix
Not deleting the pointer in the main, since it is deleted in the destructor of the VList.
#include <iostream>
using namespace std;
#include "vlist.h"
#include "video.h"
int main()
{
//Create temporary video object pointer using Video * temp = new Video(arguments);
//Pass in the temp video pointer to the list and insert it with VList function
string firstLine, secondLine, thirdLine = "";
float fourthLine = 1.1;
int fifthLine = 2;
VList list;
Video * tempVid = new Video(firstLine, secondLine, thirdLine, fourthLine, fifthLine);
list.insert(tempVid);
// delete tempVid; // don't delete this pointer right here, since I've found that you are deleting the pointer in the destructor of VList
list.print();
return 0;
}
Second Fix
You might like to use something called smart pointers as of C++11 these are standardized! See std::unique_ptr and std::shared_ptr. They will automatically delete the pointers and guarantees no memory leaks.
The second problem is that I cannot figure out how to properly access
the individual video object attributes in each node because my getter
functions (defined in video.h) won't work.
Your second problem is related to first one as your are deleting the pointer before using it which causes undefined behaviour and the output you might be getting is like a garbage. isn't it?
For the sake of simplicity I would recommend using simple Video reference not pointers. Pass them by value and all your problems will evaporate.

Answer 2

To answer my own question and that of anyone who might see this. I just needed to change it around a bit and set a temp object pointer inside of print and cout a get function onto that. It's very late so I apologize if there are any errors. I was indeed getting an address like I thought.
void VList::print() {
Node *ptr = m_head;
while (ptr != NULL) {
Video *tempPtr = ptr->m_vid;
cout << tempPtr->getTitle() << endl;
ptr = ptr->m_next;
}
}