Simple access violation example.

[jpm2mpj]

Hello everyone,

I'm not a complete beginner in computers but I took a long break from them due to life's requirements including children etc...

Anyways, I'm getting into C++ programming and the way I learn is to jump into the deep end and try to stay afloat....

Here's a very simple program and very easy to set up and follow. When I run the program, using Visual Studio 2017 IDE, I get an error as follows...."Exception thrown: read access violation. this was nullptr."

Here is the code which comprises of: Main.cpp file and 2 classes called Game and GameObject with their corresponding cpp and h files.

So.….in main I create a Game object and call the objects runGame() method.
In runGame(), I create a GameObject object, then I invoke Game objects update() method which invokes GameObject objects objUpdate which performs xPos++ and thats where I get the error.

Hope I explained that ok...

Any help would really be appreciated and a big learning curve for me....I've exhausted the google for help but cant find a specific example and solution...

Thank you all!!

Main.cpp
--------

#include "Game.h"

Game* game = new Game();

int main(int argc, char *argv[]) {

	game->runGame();

	delete game;
	game = nullptr;

	return 0;
}

------------------------------------------

Game.cpp
--------

#include "Game.h"

GameObject* player = nullptr;

void Game::runGame()
{
	GameObject* player = new GameObject(5, 5);

	update();
	render();

	delete player;
	player = nullptr;
}

void Game::update()
{
	player->objUpdate();
}

void Game::render()
{
}

------------------------------------------

Game.h
------

#pragma once

#include "GameObject.h"

class Game
{
public:
	void runGame();

	void update();
	void render();
};

------------------------------------------

GameObject.cpp
--------------

#include "GameObject.h"



GameObject::GameObject(int x, int y)
{
	xPos = x;
	yPos = y;
}


GameObject::~GameObject()
{
}

void GameObject::objUpdate()
{
	xPos++;
}

void GameObject::objRender()
{
}
------------------------------------------

GameObject.h
------------

#pragma once

class GameObject
{
public:
	GameObject(int x, int y);
	~GameObject();

	void objUpdate();
	void objRender();

public:
	int xPos;
	int yPos;
};

------------------------------------------

[Thomas1965]

Please do yourself a favor and forget about pointers and also try to avoid global variables.
The game var could be just a local var in main and player could be a member var of Game.

[jpm2mpj]

Forget about pointers, in games, lol I don't think so.....And as far as Globals are concerned, i will take that into consideration. This example was part of a bigger project I am writing......But hey, thank you for your humble opinion.....

I just solved the problem too....I am declaring player twice...…

GameObject* player = new player(5, 5);

should be....

player = new GameObject(5, 5)

[Repeater]

Forget about pointers, in games, lol I don't think so..

There's nothing special about games that mean they get a free pass. Pointers should only be used when there's no safe, sensible alternative.

In the code above, there is no good use being made of pointers.

[jpm2mpj]

The code above is just a simple example to understand pointers further....my bigger project relies more on references....

I am not declaring I know it all, i'm just diving in feet first and learning by my mistakes.....

Your replies are duly noted and very much appreciated.....it's quality advice that I have received here that will further my adventures.....

So thank you once again for your kind words of instruction, I take it all aboard..!!


kind Regards....