I have to get a project done for university but I can not figure out how it can be done.
The problem is that I want to allocate a Condition object (not a Pointer) in the GameHandler Class like in the example below, but I can not do this because I think of the included Condition.h in the Engine Class. So I am not able to include the Condition class twice. Am I wright?
What can I do to get a solution that works kind like my wrong example?
Thank you a lot!!!
Condition.h:
#ifndef CONDITION_h
#define CONDITION_h
class Condition
{
enum Rank {FIRST, SECOND, THIRD};
void doSomething();
};
#endif
Engine.h
#ifndef ENGINE_h
#define ENGINE_h
#include "Condition.h"
class Engine
{
Condition::Rank getter();
};
#endif
But now I have a third Class which should look like this where I want to create a Condition Object (not a Pointer). How can this be done?
GameHandler.h
#ifndef GAMEHANDLER_h
#define GAMEHANDLER_h
#include "Condition.h"
class GameHandler
{
Condition condition_;
condition_.doSomething();
}
#endif
By default, class members are private in C++ (more about access specifiers here). Try declaring them as public.
class Condition
{
public:
enum Rank {FIRST, SECOND, THIRD};
void doSomething();
};
Also, you cannot call a method within the declaration of a class! You'd have to do it inside a method (for example, the constructor), but the where will depend on what do you want to do.
class GameHandler
{
Condition condition_;
public:
GameHandler() {
condition_.doSomething();
}
}
Using :
#ifndef GAMEHANDLER_h
#define GAMEHANDLER_h
/.../
#endif
Will prevent multiple inclusion, so it doesn't matter if you include your header multiple times
Related
So, read clearly...
// scene.h
#include "Entity.h"
class Scene
{
public:
Entity createEntity() {
return Entity(this);
}
};
So, that was the Scene class, then we've got the Entity class
// entity.h
class Entity
{
public:
Entity(Scene* scene) {
m_handle = scene->m_registry.create() // entt library
}
};
I tried forward declaring these classes, but since they access eachothers' functions and class variables and etc, it's kinda impossible.
I was trying to create a Scene that holds Entities. Since c++ has this strange issue when two files are including each other, I don't really know what to do since my classes has to access each others' functions and variables and etc, forward declaring didn't really work...
Use pragma in each header file:
#pragma once
Or include guards:
Scene.h
#ifndef PROJECT_SCENE_H
#define PROJECT_SCENE_H
// your scene class
#endif // PROJECT_SCENE_H
Entity.h
#ifndef PROJECT_ENTITY_H
#define PROJECT_ENTITY_H
// your entity class
#endif // PROJECT_ENTITY_H
Greetings oh mighty coders,
I am a beginner and in a bit of trouble here.
There is my baseclass (sensor.h):
class sensor
{
private:
int sensor_id;
string sensor_name;
string sensor_type;
float reading;
public:
sensor();
sensor(int, char*, char*);
~sensor();
/* Few extra methods here */
};
... and I want to create 4 other classes that inherit from my baseclass sensor
(temperaturesensor, humiditysensor... and so on).
#include "sensor.h"
class temperaturesensor:public sensor
{
public:
Temperatursensor(int, char*,char*);
~Temperatursensor();
/* Few extra methods here */
};
Thing is: Every single one of these classes has to be in its own .cpp/.h file and then be included and used in my main.cpp.
using namespace std;
#include <xyz.h>
/* Other libaries here */
....
#include "temperaturesensor.h"
#include "humiditysensor.h"
int main()
{
sensor* station[2];
station [0] = new temperaturesensor(x,y,z);
station [1] = new humiditysensor(x,y,z);
}
If I include one of them it's no biggie. However: If I use multiple ones I get an redefinition error.
error C2011: 'sensor': 'class' typeredefinition
c:\users\name\desktop\project\sensor.h 14
error c2011: 'temperaturesensor' : 'class' typeredefinition
What can I do to workaround this? Note that I am not allowed to use #pragma once
Sorry for my stupidity and thanks in advance!
You must use:
#ifndef FILE_H
#define FILE_H
.. normal code here
#endif
or
#pragma once
but too, I think, that sensor schould be abstract class and you schould use virtual destructor.
One more think is that array is numerate from 0.
you forgot to use the include guards in your header class,
this is redefining your base class everytime you use it.
so, just do a
#pragma once
or a normal include guard
#ifndef YOURFILENAME_H
#define YOURFILENAME_H
.. normal code here
#endif
Then you will not have the multiple definition error.
The definition of the class sensor is coming from both "temperaturesensor.h"
and "humiditysensor.h". Use guards https://en.wikipedia.org/wiki/Include_guard or #pragma once: https://en.wikipedia.org/wiki/Pragma_once
Let's say I want to compile something like this:
//Prova.h:
//--------------------
#ifndef _PROVA_
#define _PROVA_
#include "Terza.h"
class Prova{
public:
Prova();
};
#endif
and
//Terza.h:
//--------------------
#ifndef _TERZA_
#define _TERZA_
#include "EreProva.h"
class Terza{
public:
Terza();
};
#endif
and
//EreProva.h:
//--------------------
#ifndef _EREPROVA_
#define _EREPROVA_
#include "Prova.h"
class EreProva : public Prova{
public:
EreProva();
};
#endif
which doesn't compile saying "'Prova' : base class undefined".
What is the best way to avoid recursion of header between inherited classes?
If you need to have cyclic dependencies there is something wrong with your design and you should revisit your design and try to remove such complex and unwanted cyclic dependencies.
One of overcoming cyclic dependencies is to use Forward Declarations, but note that once you forward declare a type the type becomes Incomplete type for the compiler and there are limitations about what operations you can do with it. You cannot perform any operations on that type instances which need the compiler to know the memory layout of the type.
Good Read:
When can I use a forward declaration?
Sometimes you can work around problems of this sort by tring the following: (1) try adding the "#pragma once" directive at the top of your files, although this may be compiler specific (I used it when developing in VC++ some time ago) (2) instead of including the header files in the class, you can try just add "class Prova", or whatever class it is, to indicate a class which you will define later on but want to "use" now.
Although as Als says, it is better to avoid such designs.
In this code:
//Prova.h:
//--------------------
#ifndef _PROVA_
#define _PROVA_
#include "Terza.h"
class Prova{
public:
Prova();
};
Since you don't use the Tezra class in any way, you don't need the #include. Take it out. Also, you are missing and #endif. Close the #ifndef in this file with a matching #endif in this file.
Moreover:
//Terza.h:
//--------------------
#ifndef _TERZA_
#define _TERZA_
#include "EreProva.h"
class Terza{
public:
Terza();
};
#endif
#endif
You also don't use the EreProva class in this file at all -- so take out the #include statement. You also have an extra #endif at the end of the file. There is only one #ifndef here, so there should only be one #endif. Take the last one out.
I have Environment.h file:
#include <windows.h>
#include "interfaces.h"
#ifndef ENVIRONMENT_H
#define ENVIRONMENT_H
class Environment {};
#endif
and i have Interfaces.h file:
#ifndef INTERFACES_H
#define INTERFACES_H
class IMoving {
public:
virtual void Move() = 0;
};
#endif
in interface IMoving i would like to get an Environment class, to know how to move
class IMoving {
public:
virtual void Move(Environment*) = 0;
};
if i want to do this i need to include environment.h
#include "Environment.h"
and here i'm getting an error, becouse Environment.h - includes Interfaces.h and Interfaces.h - includes Environtment.h. So how to make it work ?
Sorry for spelling mistakes
For circular dependencies one can use Forward declaration(s)
In Interfaces.h just above interface definition, forward declare Environment as follows:
class Environment;
Then when you implement IMoving in a class, you will include Environment.h in its implementation (cpp) file.
You can read more about Forward declaration here.
It looks like you misspelled the class name a few times (Environtment,Envrirontment). Could that be the origin of your issue?
Otherwise I typically use the Forwarded Declaration
I'm using Visual Studio 2008 Express edition, and keep getting the following error:
"Cascadedisplay.h(4) : fatal error C1014: too many include files : depth = 1024.
Obviously I'm doing something very wrong with include files, but I just can't see what.
Basically, I have an interface class, StackDisplay, from which I want to derive CascadeDisplay in another file:
#if !defined __BASE_STACK_DISPLAY_H__
#define __BASE_STACK_DISPAY_H__
#include <boost\shared_ptr.hpp>
#include "CascadeDisplay.h"
namespace Sol
{
class StackDisplay
{
public:
virtual ~StackDisplay();
static boost::shared_ptr<StackDisplay>
make_cascade_display(boost::shared_ptr<int> csptr)
{
return boost::shared_ptr<StackDisplay>(new CascadeDisplay(csptr));
}
};
}
#endif
and then in CascadeDisplay.h:
#if !defined __CASCADE_DISPLAY_H__
#define __CASCADE_DISPAY_H__
#include "StackDisplay.h"
#include <boost\shared_ptr.hpp>
namespace Sol
{
class CascadeDisplay: public StackDisplay
{
public:
CascadeDisplay(boost::shared_ptr<int> csptr){};
};
}
#endif
So what's up with that?
#if !defined __CASCADE_DISPLAY_H__
#define __CASCADE_DISPAY_H__
Second line should be:
#define __CASCADE_DISPLAY_H__
Same with:
#if !defined __BASE_STACK_DISPLAY_H__
#define __BASE_STACK_DISPAY_H__
Also, names that contain a double-underscore are reserved for the implementation, you are not allowed to create such names in your own code. Same goes for names that begin with a single underscore and an uppercase letter.
There is a typo in your guards
#if !defined __CASCADE_DISPLAY_H__ <--- here you have DISPLAY
#define __CASCADE_DISPAY_H__ <--- here you have DISPAY (no L!)
and yes, avoid double underscores in such names
Is #if !defined... legit? I always used #ifndef.
Either way, why does your "base" class require the reference to CascadeDisplay? That doesn't seem right. Consider replacing your call to create a new CascadeDisplay with a call to a pure virtual function in StackDisplay that your subclass must implement appropriately.
IE, something like (and forgive, I don't have a c++ compiler handy to check this):
namespace Sol
{
class StackDisplay
{
public:
virtual ~StackDisplay();
boost::shared_ptr<StackDisplay>
make_cascade_display(boost::shared_ptr<int> csptr)
{
return make_display(csptr);
}
protected:
virtual boost::shared_ptr<StackDisplay> make_display(boost::shared_ptr<int> csptr) = 0;
};
class CascadeDisplay: public StackDisplay
{
public:
CascadeDisplay(boost::shared_ptr<int> csptr){};
protected:
virtual boost::shared_ptr<StackDisplay> make_display(boost::shared_ptr<int> csptr)
{
return new CascadeDisplay(csptr);
}
};
}
I believe this solution is superior, in general, to the forward declaration because you're eliminating some tight coupling between your superclass and your subclass, and making a more generic interface besides. This lets you eliminate the #include of CascadeDisplay.h in StackDisplay.h.