I am porting a C++ project to Mac using Xcode. Now I have a class that is declared as following:
namespace poi {
class AesCipher : public SymetricCipher {
public:
AesCipher();
virtual ~AesCipher ();
//more method declarations here...
};
}
Yet Xcode will present me an error for the line of the public: statement:
C++ requires a type specifier for all declarations
I assume this has to do with the namespace but I'm not that experienced with C++.
I have no idea what this error is trying to say to me. Maybe someone has seen such an error before and could just point me in the right direction what kind of mistake I might have made.
Related
Had some issues in my code recently surrounding what I now know of as a Circular dependency. In short there are two classes, Player and Ball, which both need to use information from the other. Both at some point in the code will be passed a reference of the other (from another class that will include both .h files).
After reading up on it, I removed the #include.h files from each one and went with forward declaration. This solved the issue of being able to declare the classes in eachother, but I'm now left with an "Incomplete type error" when trying to access a passed reference to the object. There seem to be a few similar examples around, though often mixed with more complex code and hard to narrow down to the basics.
I've rewritten the code in it's simplest form (a skeleton essentially).
Ball.h:
class Player;
class Ball {
public:
Player& PlayerB;
float ballPosX = 800;
private:
};
Player.h:
class Ball;
class Player {
public:
void doSomething(Ball& ball);
private:
};
Player.cpp:
#include "Player.h"
void Player::doSomething(Ball& ball) {
ball.ballPosX += 10; // incomplete type error occurs here.
}
Any help understanding why this is the case would be greatly appreciated :)
If you will place your definitions in this order then the code will be compiled
class Ball;
class Player {
public:
void doSomething(Ball& ball);
private:
};
class Ball {
public:
Player& PlayerB;
float ballPosX = 800;
private:
};
void Player::doSomething(Ball& ball) {
ball.ballPosX += 10; // incomplete type error occurs here.
}
int main()
{
}
The definition of function doSomething requires the complete definition of class Ball because it access its data member.
In your code example module Player.cpp has no access to the definition of class Ball so the compiler issues an error.
Player.cpp require the definition of Ball class. So simply add #include "Ball.h"
Player.cpp:
#include "Player.h"
#include "Ball.h"
void Player::doSomething(Ball& ball) {
ball.ballPosX += 10; // incomplete type error occurs here.
}
Here is what I had and what caused my "incomplete type error":
#include "X.h" // another already declared class
class Big {...} // full declaration of class A
class Small : Big {
Small() {}
Small(X); // line 6
}
//.... all other stuff
What I did in the file "Big.cpp", where I declared the A2's constructor with X as a parameter is..
Big.cpp
Small::Big(X my_x) { // line 9 <--- LOOK at this !
}
I wrote "Small::Big" instead of "Small::Small", what a dumb mistake..
I received the error "incomplete type is now allowed" for the class X all the time (in lines 6 and 9), which made a total confusion..
Anyways, that is where a mistake can happen, and the main reason is that I was tired when I wrote it and I needed 2 hours of exploring and rewriting the code to reveal it.
In my case it was because a typo.
I had something like
struct SomethingStrcut { /* stuff */ };
typedef struct SomethingStruct smth;
Notice how the name of the structure is not the same one as the type definition.
I misspelled struct to strcut.
Look into your code and see wether you have some typos.
I'm working on a project in c++ and I stuck with no idea what is wrong. I've writen 4 classes and everything looked fine during work (under visual studio 2010). VS 'saw' all the definition, i could use auto-fill and sudgestions, but when I tried to compile the project it sudennly went blind. It's like I didnt include headers or something (which I did). The strange thing is there is no problem with working with those classes on VS (i can ctrl+space for hint, list of attributes and methods and all that stuff) but when i try to compile it says "ClassName" is not a type.
Quick sample of problem below:
ProButton.cpp:
#include "ProButton.h"
using namespace pGUI;
ProButton::ProButton( ... )
: ProControl( ... )
{
...
}
ProButton.h:
#ifndef __PRO_BUTTON__
#define __PRO_BUTTON__
#include <string>
#include "ProControl.h"
namespace pGUI
{
class ProButton :
public pGUI::ProControl
{
public:
//attributes
...
public:
//methods
...
};
}
#endif
but compiler says:
Error 291 error C2653: 'ProButton' : is not a class or namespace name
for this line in ProButton.cpp: ProButton::ProButton( ... )
It also says:
Error 23 error C2039: 'ProControl' : is not a member of 'pGUI'
Error 24 error C2504: 'ProControl' : base class undefined
and all similar errors for whole project. I have no idea what is wrong. Looks like my VS broke :D
Of course those (...) means there is code there, just not that important for now. I can upload all solution somewhere fi it will help.
edit//
About namespaces, all header files (classes declaration) are defined in namespace with:
namespace pGUI{
class ProClass
{
};
}
all definitions for these classes (in ProClass.cpp) are using:
using namespace pGUI;
at the beginning.
I think the problem is with order of including files.
Im not sure how this is supposed to be done. So far i have 4 classes that:
class ProGUI:
has a pointer to ProContainer
includes: ProContainer and ProControl
class ProContainer:
has pointers to: ProGUI and ProControl
class ProControl:
has a pointer to ProContainer
includes ProButton
is a base class for ProButton
class ProButton:
is a sub-class of ProControl
Those classes also uses irrlicht library and I'm not sure where to include it.
I had it included in my main file just before #include "ProGUI.h". This is also the only include in main. ProGUI.h .
//EDIT 2 -> solved
It was a problem with includes. I needed to rethink my inclusion order and add some forward declarations. Anyway that all seemed strange and took me a lot of time to figure i out. Thx for help. :)
It seems that you are using following statement:
using namespace pGUI;
Just before the class declaration:
class ProControl
{
};
Instead of using following approach:
namespace pGUI
{
class ProControl
{
};
}
The using namespace, as it says uses a namespace. You need to explicitly put something a namespace using namespace keyword followed by braces!
using namespace pGUI informs the compiler that it should look in the pGUI namespace to resolve existing names.
To declare or implement something in a namespace you need to be more specific. with either:
namespace pGUI
{
ProButton::ProButton( ... ) : ProControl( ... )
{
...
}
}
or:
pGUI::ProButton::ProButton( ... ) : ProControl( ... )
{
....
}
Personally, I consider any use of using namespace to be a lazy programmer hack that completely defeats the point of namespaces. But I digress. :)
I am trying to learn C++ by practicing with exercises from the book but I seem to have run into yet another problem. I know the ostream_withassign class is found in the iostream library and that is included but I still do not understand what I am missing in my code still. I tried std but that does not seem to work either. Any one able to please inform me on what I am missing please. Thanks in Advance!
#include "stdafx.h"
#include "Conios.h"
class ConsoleStream :public ostream_withassign, public Conios
{
protected:
char X;
char Y;
public:
ConsoleStream(void);
ConsoleStream(std::streambuf * Buffer);
void SetX(char XX);
void SetY(char YY);
ConsoleStream &operator =(std::ostream &Out);
~ConsoleStream(void);
};
Your book must be very old (in computing terms). The ostream_withassign class was a nonstandard type available in "iostream.h" back in Visual Studio 6.0. You should probably update your reference material and use something more modern as many, many things have changed in C++ since then (c. 1998). (The most recent updates were standardized this year, in fact.)
I am getting an "Expected class-name before , or ; and I dont quite get how to fix it.
Here is where the error is:
class FXHost : public CPLAT::CP_Application, public CPLAT::CP_M_Listener
{
The file is FXHost.h and CPLAT:: is obviously a namespace where CP_Application and CP_M_Listener are.
I dont see why this would be wrong. This code ran fine in Metrowerks (without the CPLAT::) but in XCode CPLAT is needed due to the way the code was written by the previous developer.
Can anyone shed some light on this error?
UPDATE: Here is a sample of the CP_Application class
template <class DOC_POLICY, class PRINT_POLICY, class UNDO_POLICY>
class CP_EXPORT CP_Application : public CP_Application_Imp
{
public:
typedef DOC_POLICY DocPolicyType;
typedef PRINT_POLICY PrintPolicyType;
typedef UNDO_POLICY UndoPolicyType;
CP_Application();
virtual ~CP_Application() throw();
It looks like the compiler hasn't seen the class declaration for the two parent classes. The first thing I would check are your include directives. Are you sure you're including header which defines the classes CP_Application and CP_M_Listener?
Maybe I missed something, but I cant figure out why Visual Studio 2008 isn't seeing the rdbuf() procedure. Here is my code:
16. #include "DebugBuffer/BufferedStringBuf.h"
17.
18. BufferedStringBuf debug_buffer(256);
19. std::cout.rdbuf(&debug_buffer);
The BufferedStringBuf class is from this page: http://www.devmaster.net/forums/showthread.php?t=7037
Which produces the following error:
...src\main.cpp(19) : error C2143: syntax error : missing ';' before '.'
All I want to do is redirect std::cout to the Visual Studio Output window using OutputDebugString()..
You're not allowed to have executable statements at file-level scope. You can declare variables, but you can't call functions as standalone statements. Move your code into a function (such as gf's answer demonstrates), and you should have no problem.
Using the example class given on that site i don't have any problem:
#include <iostream>
#include "DebugBuffer/BufferedStringBuf.h"
class DbgBuf : public BufferedStringBuf {
public:
DbgBuf() : BufferedStringBuf(255) {}
virtual void writeString(const std::string &str) {}
};
int main()
{
DbgBuf debug_buffer;
std::cout.rdbuf(&debug_buffer);
}
Note that you have to create an instance of a class that derives from BufferedStringBuf because BufferedStringBuf::writeString() is pure virtual, thus making it an abstract class - abstract classes can't be instantiated.