I'm working on an application in Qt that has to be plug-able. I've looked around for a while and suddenly came upon an example for plugins in Qt: http://doc.qt.digia.com/4.6/tools-echoplugin.html
I've changed a little something about the classes. I've added a random number generator:
randomgenerator.h:
#ifndef RANDOMNUMBER_H
#define RANDOMNUMBER_H
class RandomNumber
{
public:
~RandomNumber();
RandomNumber();
int getNumber();
};
#endif // RANDOMNUMBER_H
randomgenerator.cpp:
#include "randomnumber.h"
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
RandomNumber::RandomNumber()
{
srand(time(NULL));
}
int RandomNumber::getNumber(){
return rand() % 20;
}
Then I made a small adjustment in the plugin:
echoplugin.cpp:
#include <QtGui>
#include "randomnumber.h"
#include "echoplugin.h"
QString EchoPlugin::echo(const QString &message)
{
RandomNumber* rn = new RandomNumber();
QString a;
a.setNum(rn->getNumber());
return a;
}
Q_EXPORT_PLUGIN2(echoplugin, EchoPlugin);
It's a really simplified version of the program I'm working on. The other classes and methods of the example on the given link haven't been altered.
When I try to execute this program, I get the same error as I have with my own program:
/home/user/qt/v1/echoplugin/echoplugin: symbol lookup error: /home/user/qt/v1/echoplugin/plugins/libechoplugin.so: undefined symbol: _ZN12RandomNumberC1Ev
I ran this through c++filt, and it said that the problem lies with
RandomNumber::RandomNumber()
But I can't find any error concerning that method.
Thanks in advance!
EDIT: by this time, I've solved the problem myself and will now give the explanation for programmers who encounter the same problem.
It's actually a very simple solution: if you want to use code of headers and sourcefiles that are not in the headerfile of your interface, all you have to do is include the relative path in your .pro-file, and that includes both source-files and headerfiles.
So if I wanted to use the RandomNumber class, I'd have to add this to the .pro-file of the plugin:
HEADERS += ../randomnumber.h
SOURCES += ../randomnumber.cpp
Related
I was splitting up my program into a header and implementation file per usual, however, when I tried to run the code, I got a ton of compile errors. This seems to be an issue with my computer or IDE, but I have not seen it before. This should be relatively simple as it is for a class project.
The code is as follows:
colorPicker.h
#pragma once
class colorPicker {
private:
string colorArray[7];
public:
colorPicker();
void printAllColors();
string randomColor();
};
colorPicker.cpp
#include "colorPicker.h"
#include "stdafx.h"
#include <iostream>
#include <string>
#include <ctime>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
colorPicker::colorPicker() {
colorArray[0] = "Red";
colorArray[1] = "Green";
colorArray[2] = "Purple";
colorArray[3] = "Yellow";
colorArray[4] = "Orange";
colorArray[5] = "Indigo";
colorArray[6] = "Pink";
}
void colorPicker::printAllColors() {
for (int i = 0; i < 7; i++) {
cout << colorArray[i] << endl;
}
}
string colorPicker::randomColor() {
srand((unsigned)time(0));
int j = 0;
j = rand() % 7;
return colorArray[j];
}
main.cpp
#include "colorPicker.h"
#include "stdafx.h"
#include <iostream>
#include <string>
#include <ctime>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
int main() {
colorPicker p;
p.printAllColors();
cout << "Random Color: " << p.randomColor() << endl;
system("pause");
return 0;
}
There are 20 errors given by the compiler, however, they all seem to be stemming from two undeclared identifiers which are most definitely declared. I am at a loss for what I could possibly do to fix it, and this project is due Sunday. Thank you.
Here are the errors
Tons of Errors
You need #include "colorPicker.h" in colorPicker.cpp. Each .cpp file is handled basically independently by the compiler and they are all joined at the end by the "linker." When the compiler looks at colorPicker.cpp without an include of the corresponding header, it's at a loss as to the definition of all the classes you're working with.
There are a few things you are doing wrong. I'll just pick on a couple.
Firstly, each header file you write should be self-contained - in the sense that, if it relies on content of some other headers, it includes that header. If a compilation unit (a formal name for a source file with a .cpp in your case) includes your header, it should not have to include something else your header depends on.
Second, it is a bad idea for a header to rely on any using directive, such as using namespace std. There are plenty of explanations of that available, so I won't repeat.
To understand the above, look at colorPicker.h
class colorPicker {
private:
string colorArray[7];
public:
colorPicker();
void printAllColors();
string randomColor();
};
Firstly, this depends on string, but there is no definition of string visible in the header file. Usage of that type depends on the standard header <string>.
Second, that string type is within namespace std. So your header relies on the compilation unit (the source file that includes your header) having previously used a using directive i.e. using namespace std.
To fix these two problems, change the header to
#ifndef SOME_MACRO_UNIQUE_TO_YOUR_COLOR_PICKER_HEADER
#define SOME_MACRO_UNIQUE_TO_YOUR_COLOR_PICKER_HEADER
#include <string>
class colorPicker
{
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
#endif
(I've also done some minor changes of layout, since I have various reasons to prefer that.
However, the #include <string> means that this version will not fail to compile, as yours does, if it is included by a compilation unit that does not have #include <string>.
The usage of the fully qualified name std::string, rather than string, also means there is no dependence on the using directive using namespace std. It also means compilation errors can't be triggered in your header if your compilation unit has another using directive.
I've also used an include guard, rather than #pragma once. Although most modern compilers support #pragma once, it is actually not standard C++ (a #pragma, by definition in the standard, is a compiler-specific hook). Include guards are supported in standard C++.
If you've done that, your code should mostly compile as is. However, optionally, you may wish to
remove the using directives using namespace std from your other files. If you do that, you will need to change the definition of colorPicker::randomColor() in colorPicker.cpp so it returns the fully qualified type std::string rather than string.
Remove #include <string> from files that have #include "colorPicker.h". This is possible, since colorPicker.h now includes <string>. This step is optional, since there is no problem with including standard headers more than once in a compilation unit.
A few other notes
In C++, although it is not a major concern, it is usually considered better to use include <cstdio> and <cstdlib> rather than the C headers <stdio.h> and <stdlib.h>.
Your code is calling srand((unsigned)time(0)) whenever colorPicker::randomColor() is called. It is better to only call it once in an entire program, not in a function that may be called multiple times.
A header file should be self-contained as far as #includes go. That means that you should be able to #include the header file without having to include other stuff before it!
Your colorPicker.h does not meet that requirement. It apparently uses std::string from the standard library but does not have an #include <string> on top, so everyone who uses colorPicker.h has to remember to put an #include <string> before it. That's pretty annoying.
Even worse, colorPicker.h refers to std::string as string, which implies a using std::string; or using namespace std; somewhere before any #include "colorPicker.h" line, and both of those are very bad coding style in C++, if not used in tighter scopes.
Here's how to fix the header file:
#pragma once
#include <string>
class colorPicker {
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
As far as your *.cpp files go, I can see that you are using #include "stdafx.h". Why? It's a non-standard Microsoft thing completely unnecessary in your case. You are also using it incorrectly. It must be the first include. Just remove it entirely.
Some other suggested cleanup:
using namespace std; lines in *.cpp files is not as bad as in header files, but if I were you, I'd just get rid of it completely. Just use complete names. Say std::cout, not cout. And so on. It's just the most consistent way and it avoids a lot of trouble.
You include a lot of headers which you don't need. For example, what's <ctime> for?
Don't use system("pause");. Do not look for artificial ways of pausing a command-line program.
You may need add head file and in colorPicker.h.
And the std namespace is needed while using string.
BTW, the header guards is recommended strongly.
#ifndef COLOR_PICKER_H
#define COLOR_PICKER_H
#pragma once
#include <string>
class colorPicker {
private:
std::string colorArray[7];
public:
colorPicker();
void printAllColors();
std::string randomColor();
};
#endif
I am having trouble tracking down the source of this error because all other Lua appears to be compiling fine.
My scriptManager class is like so:
#include <luabind\lua_include.hpp>
//skip some
LuaScriptManager::LuaScriptManager()
{
state = luaL_newstate(); //is recognised fine
luaL_openlibs(state); //will not compile with this not commented
}
Luabind\lua_include.hpp is like so:
#ifndef LUABIND_CPLUSPLUS_LUA
extern "C"
{
#endif
#include "lua.h"
#include "lauxlib.h"
#include "luaconf.h"
#ifndef LUABIND_CPLUSPLUS_LUA
}
#endif
I don't believe I am missing any #include files that would apply to LuaL_openLibs. However, I didn't set up the lua files for this, someone else on the team did. Does anyone know any potential causes for this, or is my best bet to nuke it and set up the lua include files from scratch?
Hi I was just trying to learn separate Classes in C++. I don't know why my code is not working.
So here is the main file code
#include <iostream>
#include "Number.h"
using namespace std;
int main()
{
Number key;
key.setNumber(200);
cout<<key.getNumber();
return 0;
}
Here is the Class cpp functions file code
#include "Number.h"
#include <iostream>
using namespace std;
void Number::setNumber(int transfernumber)
{
privatenumber = transfernumber;
}
int Number::getNumber()
{
return privatenumber;
}
And here is the header file
#ifndef NUMBER_H
#define NUMBER_H
class Number
{
public:
Number();
void setNumber(int transfernumber);
int getNumber();
private:
int privatenumber;
};
#endif // NUMBER_H
Thanks
In your cpp file you need to define the default constructor for the Number class. For example:
Number::Number() : privatenumber(0) {}
I have test your example. The error happened for the main.cpp cannot found the number.cpp. You have three ways to solve it:
write your main() to the number.cpp, not a solo file.
complie the main.cpp with the linux command gcc or write a Makefile, instead of using codeblocks.
If you want to use the codeblocks for compiling, you should create a project, and then add your three files to the project. Now compile the main.cpp.
Use the three ways above, I think you will compile successfully.
BTW, you should add the Number::Number() 's implementation.
I am writing a plugin for Autodesk Maya using C++ and have a linker error.
My main class is Maya_Search_Plugin.cpp
#include <Utilities.h>
DeclareSimpleCommand( search_face, PLUGIN_COMPANY, "4.5");
//doIt method is entry point for plugin
MStatus search_face::doIt( const MArgList& )
{
//calls to Maya types/functions and Utilities functions
}
Then I have a Utilities class containing some static methods with header looking like this
#ifndef __Maya_CPP_Plugin__Utilities__
#define __Maya_CPP_Plugin__Utilities__
//#pragma once
//standard libs
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <iostream>
#include <math.h>
//maya libs
#include <maya/MDagPath.h>
#include <maya/MFn.h>
#include <maya/MFileIO.h>
#include <maya/MIOStream.h>
#include <maya/MFnMesh.h>
#include <maya/MFnTransform.h>
#include <maya/MGlobal.h>
#include <maya/MSelectionList.h>
#include <maya/MSimple.h>
#include <maya/MTypes.h>
#include <maya/MPointArray.h>
#include <maya/MObjectArray.h>
class Utilities{
public: static const int max_mov = 50;
public:
static double get_mesh_error(MPointArray, MPointArray, int);
static MStatus translateManipulator(double amount, MObject *path);
static void GetSelected(MObjectArray* objects, MFn::Type type);
};
#endif /* defined(__Maya_CPP_Plugin__Utilities__) */
with the implementation like this
#include <Utilities.h>
double Utilities::get_mesh_error(MPointArray a, MPointArray b, int vertexCount){
...
}
MStatus Utilities::translateManipulator(double amount, MObject *path){
...
}
void Utilities::GetSelected(MObjectArray* objects, MFn::Type type) {
...
}
However I am getting the following error
duplicate symbol _MApiVersion in:
/Users/tmg06qyu/Library/Developer/Xcode/DerivedData/Maya_CPP_Plugin-hjrwvybwlvqyyscbmixdkcpdzjqr/Build/Intermediates/Maya_CPP_Plugin.build/Debug/Maya_CPP_Plugin.build/Objects-normal/x86_64/Maya_Search_Plugin.o
/Users/tmg06qyu/Library/Developer/Xcode/DerivedData/Maya_CPP_Plugin-hjrwvybwlvqyyscbmixdkcpdzjqr/Build/Intermediates/Maya_CPP_Plugin.build/Debug/Maya_CPP_Plugin.build/Objects-normal/x86_64/Utilities.o
ld: 1 duplicate symbol for architecture x86_64
Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ld failed with exit code 1
Which I presume is a linking error and there is some circular reference somewhere, but I can't work out where it is.
Any help appreciated.
Thanks.
I know this is a year old. But I stumbled on this again a couple minutes ago...
Add
#define MNoVersionString
#define MNoPluginEntry
#include <maya/MFnPlugin.h>
to your header or cpp files where you wrote your plugin code. Include
#include <maya/MFnPlugin.h>
directly in your main.cpp that initializes the plugin.
Most of the examples in maya have the following string:
// This is added to prevent multiple definitions of the MApiVersion string.
#define _MApiVersion
before including anything. For example here.
The issue may happen if you have multiple files which include MFnPlugin.h
After fixing the previous problem (see my one other question that I have asked). I had declared more classes.
One of these is called CombatAdmin which does various things: (Header file)
#ifndef COMBATADMIN_H
#define COMBATADMIN_H
#include <string> // Need this line or it complains
#include <Player.h>
#include <Sound.h>
#include <Enemy.h>
#include <Narrator.h>
using namespace std;
class Enemy;
class Player;
class CombatAdmin // Code yet to be commented here, will come soon.
{
public:
CombatAdmin();
void healthSet(double newHealth, string playerName);
void comAdSay(string sayWhat);
void playerFindsChest(Player *player,Weapon *weapon,Armour *armour);
void youStoleOurStuffEncounter(Player *player);
void comAdWarning(string enemyName);
void comAdAtkNote(string attack, double damage,string target,string aggresor);
void entDefeated(string entName);
void comAdStateEntHp(string ent, double hp);
void comAdStateScanResults(string enemyName, double enemyHealth);
string doubleToString(double number);
string intToString(int number);
bool isRandEncounter();
void randomEncounter(Player *player,Sound *sound,Narrator *narrator);
bool combatRound(Player *player, Enemy *enemy, Sound *sound, bool ran);
void playerFindsItem(string playerName,string itemName,double itemWeight,double playerWeight);
void playerFindsGold(string playerName,double coinCnt,double playerCoinCnt);
};
#endif // COMBATADMIN_H
It is then instanced in the main.cpp file like this: (Snippet of the main.cpp file)
#include <iostream> // Required for input and output
#include <Item.h> // Item header file.
#include <Weapon.h> // Header files that I have made for my classes are needed for this program
#include <sstream> // Needed for proper type conversion functions
#include <windows.h> // for PlaySound() and other functions like sleep.
#include <time.h> // Needed to seed the rand() function.
#include <mmsystem.h> // Not sure about this one, possibly defunct in this program.
#include <stdio.h> // Needed for a similar kind of output as iostream for various functions error msgs.
#include <irrKlang.h> // The header file of the sound lib I am using in this program.
#include <Narrator.h> // The narrators's header file.
#include <Pibot.h> // Other header files of classes.
#include <Armour.h>
#include <Player.h>
#include <Weapon.h>
#include <CombatAdmin.h>
using namespace irrklang;
using namespace std;
// Forward referenced functions
void seedRandom(); // Seeds the random number so it will be random as apposed to pseudo random.
string getPlayerName(string temp); // Gets the player's new name.
int main(int argc, char* argv[])
{
// Variables and object pointers declared here.
CombatAdmin *comAd = new CombatAdmin(); // Handles combat.
Narrator *narrator = new Narrator(); // The Narrator that says stuff
Pibot *piebot = new Pibot(); // PIbot, the player's trusty companion
string temp; // Temp string for input and output
However, when I try to compile the project, I get the following error:
C:\Documents and Settings\James Moran.HOME-B288D626D8\My Documents\C++ projects\Test Project\main.cpp|59|undefined reference to `CombatAdmin::CombatAdmin()'|
I am using the Code::Blocks IDE (ver 10.05), with the GNU GCC compiler. The project is of type "Console application". I am using windows XP 32 bit SP3.
I have tried changing to search directories to include where the object files are, but no success there.
As can be seen from the code, the narrator and PIbot are instanced just fine. (then used, not shown)
My question is, therefore, what do I need to do to stop these errors occurring? As when I encountered similar "Undefined reference to x" errors before using libraries. I had just forgotten to link to them in Code::Blocks and as soon as I did, they would work.
As this class is of my own making I am not quite sure about this.
Do say if you need more information regarding the code etc.
You have declared the default constructor (CombatAdmin()) and thus prevented the compiler from automatically generating it. Thus, you either need to 1) remove declaration of the default constructor from the class, or 2) provide an implementation.
I had this kind of error and the cause was that the CombatAdmin.cpp file wasn't selected as a Build target file: Prject->Properties->Build targets
Are you sure you've to include your header as:
#include <CombatAdmin.h>
?
I think you need to include your header file as:
#include "CombatAdmin.h"
And same for other headers written by you, like these:
#include "Armour.h"
#include "Player.h"
#include "Weapon.h"
//and similarly other header files written by you!
See this topic:
What is the difference between #include <filename> and #include "filename"?
My solution was just to add a line in the header before the class defenition:
class CombatAdmin;