C++ Passing Reference of class to another class - c++

I've been trying to pass my Graphics Manager class to both my Robot and Room class.
But when attempting to pass the class by reference I get 3 errors regarding the pass by reference.
These are the errors I'm referring to:
C2143 syntax error: missing ';' before '*'
C4430 missing type specifier - int assumed. Note: C++ does not support default-int
C2238 unexpected token(s) preceding ';'
I have attempted to change the way I've been passing the classes but with no luck, I have highlighted the areas in which is causing the error as well as the code that i have tried to use to fix the problem.
Any advice in how i could go about fixing these errors is highly appreciated.
I have not included the full .cpp files as they are quite large but I will include a link to a pasteBin with the full script.
GrapicsManager.h
#pragma once
#include <iostream>
#include <SFML/Graphics.hpp>
#include "Room.h"
#include "Robot.h"
class GraphicsManager
{
public:
Room* room; //This does not Flag Up Errors
Robot* robot; //This does not Flag Up Errors
Robot.h
#pragma once
#include <iostream>
#include <SFML/Graphics.hpp>
#include <SFML/System/String.hpp>
#include "GraphicsManager.h"
//#include "Room.h" //This what i had
class Room; //This is what i changed
//class GraphicsManager; //Wasnt sure if i should use it this
//way
class Robot
{
public:
//Graphics Variables
Room* room; //This works after the change
Robot* robot; //This works after the change
GraphicsManager *gm; //This throughs up the error
//This Is what i attemped to use with no effect
//GraphicsManager* gm = new GraphicsManager(room, robot);
Robot.cpp https://pastebin.com/Xd1A3Vii
#include "Robot.h"
Robot::Robot()
{
gm = new GraphicsManager(room, robot); //This tells me gm is
//not declared
this->room = room; //This does not flag up errors
this->robot = robot; //This does not flag up errors
//Room &room = *rm; // attempted to use this but decided not
//to
}
Room.h
#pragma once
#include <SFML/Graphics.hpp>
#include <SFML/System/String.hpp>
#include "GraphicsManager.h" //
//#include "Robot.h" //what i orginally had
//class GraphicsManager; //i decided not to do it this way
class Robot; //What i changed it to
class Room
{
public:
//Reference to other classes
Room* room; //This doesnt throw errors
Robot* robot; //This doesnt throw errors
//Refference to graphics manager
GraphicsManager *gm; //This throws the three errors mentioned
};
Room.cpp https://pastebin.com/6R6vnVfy
#include "Room.h"
Room::Room()
{
gm = new GraphicsManager(room, robot);
this->room = room;
this->robot = robot;

It's the classic cicular include issue. GrapicsManager.h includes Room.h and Robot.h which each include GrapicsManager.h again. Now, for example, when compiling GraphicsManager.cpp you include GrapicsManager.h. But before you ever get to the GraphicsManager class definition, you first include Room.h. From there you go straight to include GrapicsManager.h again, but since you have a #pragma once in there, the compiler will simply skip that include. By the time the compiler then gets to the GraphicsManager *gm; member declaration in Room.h, is has never seen a declaration of a type named GraphicsManager. The error message that Visual C++ gives you then
C4430 missing type specifier - int assumed. Note: C++ does not support default-int
is arguably a bit unintuitive. At the point where it encounters the identifier GraphicsManager, an identifier can only mean the start of a declaration. Since GraphicsManager is not a known type, the compiler assumes that identifier must be the name of the entity that is supposed to be declared and you just forgot to specify the type. That's why you get the error message you see. C in the olden days used to allow you to omit the type specifier in a declaration which would just mean to use int as a default. So you would see this error as a result of trying to compile ancient, non-standard C code. That's why the error message contains the explicit note that that's not allowed…
You already added forward declarations for Room in Robot.h and for Robot in Room.h. You'll have to do the same for GraphicsManager…

Related

TypeDef error between classes C++

Im a fairly new programmer so I may not be understanding typedef correctly.
I have 2 classes Enemy.cpp and AI.cpp.
My AI.cpp needs values from Enemy.cpp to be able to process its movements etc. In AI.cpp I hold pointers to values such as position, speed and an enum for the direction the enemy is facing.
The Errors I get are listed below. If there is a more simple way to link an enum variable between classes, im all ears.
below is a working example of the error.
///////MAIN.H/////////////
#ifndef _MAIN_H_
#define _MAIN_H_
#endif // ! _MAIN_H_
///////////////////////////
////////MAIN.CPP///////////
#include "AI.h"
#include "Enemy.h"
int main(int argc, char* args[])
{
Enemy enemy;
}
//////////////////////////////
//////////ENEMY.H///////////////
#ifndef _ENEMY_H_
#define _ENEMY_H_
#include "AI.h"
class Enemy
{
public:
Enemy();
enum Facing
{
LEFT = 0,
RIGHT
};
protected:
AI* EnemiesAI;
//try this as a pointer
Facing EnemyDirection;
};
#endif
//////////////////////////////////
///////////ENEMY.CPP////////////////
#include "Enemy.h"
Enemy::Enemy()
{
EnemiesAI = new AI;
EnemiesAI->LinkEnemyToAI(&EnemyDirection);
}
////////////////////////////////////
/////////////////AI.H//////////////
#ifndef _AI_H_
#define _AI_H_
#include "Enemy.h"
class AI
{
public:
/*this needs to be a pointer, otherwise I have to pass the
value into AI on every update*/
typedef Enemy::Facing *ThisFacing; //Error 3
void LinkEnemyToAI(ThisFacing facing);
private:
//This is a pointer to a Enemy::Facing object
ThisFacing mFacing;
};
#endif
///////////////////////////////////////
////////////////AI.CPP/////////////////
#include "AI.h"
void AI::LinkEnemyToAI(ThisFacing facing)
{
mFacing = facing;
}
////////////////////////////////////////
Error C2653 'Enemy': is not a class or namespace name ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\ai.h 11
Severity Code Description Project File Line
Error C4430 missing type specifier - int assumed. Note: C++ does not support default-int ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\ai.h 11
Severity Code Description Project File Line
Error C3646 'mFacing': unknown override specifier ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\ai.h 17
Severity Code Description Project File Line
Error C4430 missing type specifier - int assumed. Note: C++ does not support default-int ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\ai.h 17
Severity Code Description Project File Line
Error C2660 'AI::LinkEnemyToAI': function does not take 1 arguments ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\enemy.cpp 7
Severity Code Description Project File Line
Error C2061 syntax error: identifier 'ThisFacing' ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\ai.h 13
Severity Code Description Project File Line
Error C2238 unexpected token(s) preceding ';' ExampleOfTypeDefError c:\dev\projects\exampleoftypedeferror\exampleoftypedeferror\enemy.h 23
Using include-guards here doesn't help really, because Enemy.h depends on AI.h which depends on Enemy.h and so on forever.
You have to break that chain, and the easiest way to break it is through something called forward declarations.
If you look closer in the Enemy.h header file, all it uses of the AI class is to declare a member variable which is a pointer to AI. That means you don't need the full definition of AI, you only need to tell the compiler that the class AI exists. Something like
#ifndef ENEMY_H
#define ENEMY_H
class AI; // Forward declaration of the AI class
class Enemy
{
public:
Enemy();
enum Facing
{
LEFT = 0,
RIGHT
};
protected:
AI* EnemiesAI;
//try this as a pointer
Facing EnemyDirection;
};
#endif // ENEMY_H
Now in the Enemy.cpp file you still need to #include "AI.h" since the full definition of the class is needed there.
This forward declaration isn't really possible in the AI.h header file, since in it you use the enumeration Enemy::Facing. However, since Enemy.h no longer includes AI.h there's no longer the circular dependency.
Also note that I changed the header guard macro to not have leading underscores, since all symbols with a leading underscore follower by an upper-case letter is reserved in all scopes. See e.g. this question and its answers for more details.

Having linking classes issue? c++ I have no clue what is up

I have three classes.
first class:
#ifndef C_LINKED_LIST_H
#define C_LINKED_LIST_H
class CLinkedList {
private:
//removed code for brevity
public:
// removed code for brevity
};
#endif
second class:
#ifndef C_SSF_FOLDER_CONTAINER_H
#define C_SSF_FOLDER_CONTAINER_H
#include "C_SSF_Folder.h"
#include "CLinkedList.h"
class C_SSF_Folder_Container {
private:
// removed code for brevity
public:
int Add_Folder(C_SSF_Folder *_pcl_SSF_Folder);
C_SSF_Folder *Get_Folder(int _i_Index);
C_SSF_Folder *Get_Folder(char *_pch_Name);
//^-----errors
};
#endif C_SSF_FOLDER_CONTAINER_H
my third class
#ifndef C_SSF_FOLDER_H
#define C_SSF_FOLDER_H
#include <windows.h>
#include <fstream>
#include "C_SSF_Folder_Container.h"
using namespace std;
class C_SSF_Folder {
public:
private:
C_SSF_Folder_Container cl_SSFFC_Folder_Container;
public:
};
#endif
my third class C_SSF_Folder.
I am including "C_SSF_Folder_Container.h"
and declaring a C_SSF_Folder_Container container.
Before declaring the variable it compiles fine. After I declare it
I get syntax errors in my C_SSF_Folder_Container
Severity Code Description Project File Line Suppression State
Error C2061 syntax error: identifier 'C_SSF_Folder' CSSFileSystem\projects\cssfilesystem\cssfilesystem\c_ssf_folder_container.h 16
Error C2061 syntax error: identifier 'C_SSF_Folder' CSSFileSystem \projects\cssfilesystem\cssfilesystem\c_ssf_folder_container.h 19
As I myself look into it I think there is a problem because my C_SSF_Folder is including C_SSF_Folder_Container.
and C_SSF_Folder_Container is including C_SSF_Folder
but the defines should take care of it? Other than that I have no clue what's the problem.
Everything is typed correctly.
You've got a circular #include -- C_SSF_Folder_Container.h #includes C_SSF_Folder.h and C_SSF_Folder.h #includes C_SSF_Folder_Container.h.
This would cause an infinite regress (and a compiler crash) except that you've got the #ifndef/#define guards at the top of your files (as you should); and because of them, instead what you get is that one of those two .h files can't see the other one, and that's why you get those errors.
The only way to fix the problem is to break the circle by deleting one of the two #includes that comprise it. I suggest deleting the #include "C_SSF_Folder.h" from C_SSF_Folder_Container.h and using a forward declaration (e.g. class C_SSF_Folder; instead.
C_SSF_Folder.h and C_SSD_Folder_Container.h are including each other(Circular Dependency).
When the compiler compiles C_SSF_Folder_Container object, it needs to create a C_SSF_Folder object as its field, however, the compiler needs to know the size of C_SSF_Folder object, so it reaches C_SSF_Folder object and tries to construct it. Here is the problem, when the compiler is constructing C_SSF_Folder object, the object has a C_SSF_Folder_Container object as its field, which is a typical chicken and egg question, both files depends on each other in order to compile.
So the correct way to do it is to use a forward declaration to break the circular dependency(including each other).
In your C_SSF_Folder.h, make a forward declaration of C_SSF_Folder_Container.
#include <windows.h>
#include <fstream>
using namespace std;
class C_SSF_Folder_Container;
class C_SSF_Folder {
public:
private:
C_SSF_Folder_Container cl_SSFFC_Folder_Container;
public:
};
#endif
Finally, include C_SSF_Folder_Container.h in your C_SSF_Folder.cpp.
You can also learn more in the following links:
Circular Dependency (Wiki):
https://en.wikipedia.org/wiki/Circular_dependency
Forward Declaration by Scott Langham
What are forward declarations in C++?

C++ Include guards

I know this been asked a number of times but no answers seem to solve this.
I have two files.
Main.cpp
#include <irrlicht\irrlicht.h>
#include <vector>
#include <string>
#include <iostream>
#include "Scene.h"
#include "Camera.h"
#include "Gui.h"
irr::IrrlichtDevice* device;
irr::video::IVideoDriver* driver;
int main() {
device = irr::createDevice(irr::video::EDT_SOFTWARE, irr::core::dimension2d<irr::u32>(640, 480), 16, false, false, false, 0);
if (!device)
return 1;
device->setWindowCaption(L"NeoTrap");
driver = device->getVideoDriver();
sceneManager = device->getSceneManager();
GUIEnvironment = device->getGUIEnvironment();
//Testing
Mesh* ground = new Mesh();
//Testing
while (device->run()) {
driver->beginScene(true, true, irr::video::SColor(255, 120, 102, 136));
sceneManager->drawAll();
GUIEnvironment->drawAll();
driver->endScene();
}
device->drop();
return 0;
}
Scene.h
#ifndef _SCENE_HEADER_
#define _SCENE_HEADER_
irr::scene::ISceneManager* sceneManager;
struct Mesh {
public:
Mesh();
private:
};
class Scene {
public:
Scene();
private:
};
#endif
What I am trying to do is declared a variable in Scene.h and define it from within the main function. I am not sure if I don't understand include guards, but I am getting weird errors:
'irr': is not a class or namespace name
syntax error: missing ';' before '*'
missing type specifier - int assumed. Note: C++ does not support default-int
but when I move the following line back in the Main.cpp file
irr::scene::ISceneManager* sceneManager;
the program compile. When am I not able to declare it in scene.h and set the value from the main function?
It's best to not declare variables in headers. It ends badly far more often than not because every file that includes the header will make their very own sceneManager. When the linker comes along to put the program together it may find dozens of sceneManagers all with an equal claim to being the real sceneManager, throw its hands up in disgust, and spray error messages all over the console.
In scene.h add
#include <irrlicht\irrlicht.h>
up at the top to declare all the bits and bobs of irrlicht so that they are available in scene.h.
Then change
irr::scene::ISceneManager* sceneManager;
to
extern irr::scene::ISceneManager* sceneManager;
extern tells the compiler that sceneManager exists and storage will be allocated somewhere else. The compiler smiles and carries on, leaving sorting out where the one, true sceneManager is to the linker.
Finally, put
irr::scene::ISceneManager* sceneManager;
in Main.cpp to allocate storage so that the linker has a sceneManager to find.
Documentation on extern
Recomended reading: When to use extern in C++
You are declaring that sceneManager is of type irr::scene::ISceneManager*, but the irr namespace doesn't exist when you are declaring that variable. Add an include to the header file that declares that namespace before declaring your variable.
After that, you'll need to declare sceneManager to be extern in the header so that each compilation unit that includes that header doesn't create its own instance of the variable. Then because it is extern, you will also want to redeclare it (without extern) in main.cpp.

C++ Issues creating class objects and circular inclusion

This is my first question, so I apologize in advance for any things about stack overflow that I may not be aware of!
The issue I am having is that I am making a simple SDL program, currently it is just supposed to draw a PNG image (Assets/Board.png) to the screen, but I am being faced with many errors to do with the two classes communicating with each other, I think that I have circular inclusion errors. But I have been trying to fix the problem for days and I haven't been able to solve it.
Here are the errors that I am getting:
http://imgur.com/gallery/vq3XLwU/new
(Here is a text version of it, but the formatting is bad sorry)
1>d:\code\c++\games\chess\chess\manager.h(41): error C2079: 'Manager::Tex' uses undefined class 'Render'
1>d:\code\c++\games\chess\chess\render.h(32): error C2146: syntax error : missing ';' before identifier 'manager'
1>d:\code\c++\games\chess\chess\render.h(32): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>d:\code\c++\games\chess\chess\render.h(32): error C2146: syntax error : missing ';' before identifier 'manager'
1>d:\code\c++\games\chess\chess\render.h(32): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
(I have used an image because the formatting of the image is easier to read.)
(Also click on the image in imgur to see the zoomed in version)
You can download the entire code project here (ZIP FILE):
https://www.mediafire.com/?og21315fc1d58sk
But here is the code that I think is causing the issues:
(Manager.h file)
//Include guards.
#pragma once
//Headers.
#include "Render.h"
//Librarys.
#include <SDL_image.h>
#include <string>
#include <SDL.h>
//Namespaces.
using namespace std;
//Enumerator.
enum State { Play, Exit };
class Manager
{
public:
Manager(); //Constructor.
~Manager(); //Destructor.
//Rendering.
SDL_Window* Window;
SDL_Surface* Screen;
SDL_Renderer* Renderer;
//Functions.
void Run();
void Init();
void Close();
void Input();
void Update();
void Error(string);
//Game variables.
State state;
Render Tex;
private:
//Constant values.
const int WINDOW_POS_X = SDL_WINDOWPOS_CENTERED;
const int WINDOW_POS_Y = SDL_WINDOWPOS_CENTERED;
const int INIT_FLAGS = SDL_INIT_VIDEO;
const int SCREEN_HEIGHT = 600;
const int SCREEN_WIDTH = 600;
};
(And here is the Render.h file)
//Include guards.
#pragma once
//Headers.
#include "Manager.h"
//Librarys.
#include <SDL_image.h>
#include <string>
#include <SDL.h>
//Namespaces.
using namespace std;
class Render
{
public:
Render(); //Constructor.
~Render(); //Destructor.
//Functions.
void Draw(int, int); //Draws texture at position.
void Load(string); //Loads texture from path.
void Deallocate(); //Destroy texture.
//Getter functions.
int GetHeight() { return Height; };
int GetWidth() { return Width; };
private:
SDL_Texture* Texture; //Actual image.
Manager manager; //Manager class.
int Height; //Height of image.
int Width; //Wdith of image.
};
So in conclusion, I am having errors related to the class objects, which I believe are being caused by circular inclusion, despite my research I have not been able to fix these issues. I would greatly appreciate any help with this issue.
P.S I know I am not supposed to use the std namespace, instead I must write std::foo, I am aware, so please don't comment about it!
In C++ "ownership" is a very important concept. A class "owns" its members. The problem is you have two objects and you've told the compiler that both "own" the other, which won't do. You have to decide which of them owns the other, and has it as a member (or maybe neither owns the other). At least one class must refer to the other, rather than listing it as a child/member. And the best sort of reference is a pointer.
class Manager;
// this forward declaration tell the compiler the class exists, but
// we don't care about the details yet, so we won't include the header.
// if we try to include it, that header refers to Render, which the compiler
// hasn't seen yet, so the compiler will fail.
class Render
{
public:
Render(Manager* parent_); //Constructor.
...stuff...
Manager* parent;
};
Cpp file:
#include "manager.h"
#include "render.h"
Render::Render(Manager* parent_)
: parent(parent_)
{}
SUGGESTIONS:
1. Eliminate the "Render.h" include:
There doesn't seem to be anything in "Manager.h" that needs anything in "Render.h" - so why include it?
Similarly, 2. Eliminate the "Manager.h" include.
You can simply use a "forward declaration", instead of including the whole class interface (.h file).
These links might help:
C++ circular include
Headers and Includes: Why and How
Okay, I think that I have solved the problem, thanks to a variety of comments. The solution may not be ellegant but it works. Instead of defining the Render Tex variabel inside the Manager header, I declared it inside the Manager.cpp class. Once I had done that I can #include "Render.h" inside the Manager .cpp file. I dont know if that explanation is clear but here is the top of the manager.h file:
//Include guards.
#pragma once
//Librarys.
#include <SDL_image.h>
#include <string>
#include <SDL.h>
And here is the top of the Manager.cpp file:
//Header.
#include "Manager.h"
#include "Render.h"
//Librarys.
#include <iostream>
//Objects.
Render Tex;

C2065: 'class' undeclared identifier, header included

I wanted to run the game by testing the spawner. I thought that I had properly declared the Spawner class by calling its header file in SceneGame.hpp
When I wanted to use the Spawner* as a vector variable, I thought there would be no compiler errors, but I was wrong.
The source of the error comes from declaring the variable vector spawner_list
Relevant files:
Spawner.hpp
#pragma once
#include <SFML\Graphics.hpp>
#include "weapon.hpp"
#include "movement.hpp"
// forward declare
class EnemyTemplate;
/*
Spawner will create enemies and/or power ups
For spawning enemies, they will recieve one weapon and one movement type
for powerups, only one will spawn and the spawner would disappear afterwards
The spawner will create entities through the following:
Spawn gap: the amount of time to wait between making enemies, in frame ticks
Spawn limit: the amount of enemies to make before being removed
*/
class Spawner{
private:
int spawnGapTime;
int spawnGapSet;
// If you plan to spawn finite enemies, then use constructor
int spawnLimit = -1;
EnemyTemplate* enemyData;
Weapon* givenWeapon;
Movement* givenMovement;
int ticks;
public:
Spawner(Weapon*, Movement*, EnemyTemplate*, std::vector <int>);
void update();
void spawn_enemy();
void spawn_count();
~Spawner(){
delete givenWeapon;
delete givenMovement;
delete enemyData;
};
};
SceneGame.hpp
#pragma once
#include <SFML\Graphics.hpp>
#include "scene.hpp"
#include "game.hpp"
#include "entity.hpp"
#include "movement.hpp"
#include "weapon.hpp"
#include "player.hpp"
#include "collisionGrid.hpp"
#include "spawner.hpp"
// forward declare
class BulletTemplate;
class SceneGame : public Scene{
private:
// skipping some code
std::vector <Spawner*> spawner_list; // The source of the error
public:
SceneGame(Game* game);
// skipping some code
};
Is there any way I can fix this undeclared identifier problem without having to forward declare Spawner?
C2065: 'class' undeclared identifier
If that is the literal text of the error message, you're compiling as C, not as C++.
If it isn't the literal text of the error message, you should have posted the literal text of the error message.