I have this code:
#ifndef AI_H
#define AI_H
void BuildTree(Board b);
int getMove();
void acceptMove(int);
#endif
and the cpp file:
#include "AI.h"
#include "Board.h"
void BuildTree(Board b)
{
}
int getMove()
{
return 0;
}
void acceptMove(int)
{
}
I am getting an error because of the paramater Board b in the header file.
the error is:
Error 1 error C2065: 'Board' : undeclared identifier
why is it not accepting an object?? I want the function to receive an object by value, not reference.
Just include Board.h in ai.h:
#ifndef AI_H
#define AI_H
#include "Board.h"
void BuildTree(Board b);
int getMove();
void acceptMove(int);
#endif
The compiler is complaining about Board: it does not know what is it. You must define (not only declare) it to be able to use an object of that type (e.g. taking it as parameter).
You can solve your issue by #includeing the header file defining Board :
#include "Board.h"
Include Board.h in your first file, AI.h
Related
Hey guys so I am working on a Hash program in C++ for my class. I am using a template T class for my header file and when I try to call the class constructor from main it gives me a undeclared identifier and type 'int' unexpected error. Here is my HashTable.h file:
#pragma once
#include "Record.h"
#define MAXHASH 1000
#ifndef HASHTABLE_H
#define HASHTABLE_H
using namespace std;
template <class T> class HashTable
{
public:
HashTable();
~HashTable();
bool insert(int, T, int&);
bool remove(int);
bool find(int, T&);
float alpha();
private:
int key;
T value;
};
#endif
and here is my main:
#include "HashTable.h"
#include "stdafx.h"
#include <string>
#include <iostream>
using namespace std;
int main()
{
HashTable<int> *test = new HashTable<int>();
return 0;
}
Here's the constructor in the .cpp file as well:
#pragma once
#include "stdafx.h"
#include "HashTable.h"
#include "Record.h"
#define HASHTABLE_CPP
#ifndef HASTABLE_CPP
template <class T>
HashTable<T>::HashTable()
{
Record hashArray = new Record[MAXHASH];
for (int i = 0; i < MAXHASH; i++)
{
hashArray[i]->key = 0;
hashArray[i]->value = NULL;
}
}
The specific errors I am getting are:
Error C2062 type 'int' unexpected identifier
Error C2065 'HashTable': undeclared identifier
Both the errors point to the call line in main.
It is difficult because I can't test my program until I can get this test hash to work. Any input on how to fix this issue would be awesome!
the old Microsoft application file extensions interface "stdafx.h" has to be the first directive listed if the pre-compiled header is used. It actually works best because VS expects it...I always use it.
I have the following header helper.h:
#ifndef ADD_H
#define ADD_H
class Helper{
public:
static float calculateSpriteSize(float imgSize, float screenSize);
};
#endif
This is my helper.cpp:
#include "block.h"
#include "helper.h"
float Helper::calculateSpriteSize(float imgSize, float screenSize)
{
return ((imgSize/screenSize)*100);
}
But, for some reason, when I call my function calculateSpriteSize on my running code by doing:
#include "header.h"
int main(void){
float h = Helper::calculateSpriteSize( 168.0f, 170.0f );
)
I get the following error:
error: incomplete type 'Helper' used in nested name specifier
Any help would be appreciated.
Block.h looks as follows:
#ifndef ADD_H
#define ADD_H
class Block{
private:
int imgID;
int life;
float price;
public:
Block();
void setImgID(int imgID);
int getImgID();
};
#endif
And block.cpp looks as follows:
#include "block.h"
Block::Block()
{
}
void Block::setImgID(int imgID)
{
this->imgID = imgID;
}
int Block::getImgID()
{
return imgID;
}
UPDATE: I added Helper to the class definition as suggested by Rakete1111. This did not fix the issue though.
UPDATE 2: Changed forward declaration to include. Added other include that was in my code in case its important.
The type introduced by forward declaration is incomplete type. But member function invoking requires the type to be complete, otherwise how does the compiler know whether the member exists or not, and its signature?
You need to include the header file.
#include "helper.h"
int main(void){
float h = Helper::calculateSpriteSize( 168.0f, 170.0f );
)
EDIT
You're using the same macro ADD_H in both "block.h" and "helper.h". It means for
#include "block.h"
#include "helper.h"
the second including would fail, the content of helper.h won't be included at all.
Change the including guard macro name to be unique, better to make it conform to the name of file name. Such as HELPER_H and BLOCK_H.
I have already checked StackOverflow to find the solution to my problem, but I think I might be missing something. I am trying to define a class in a header file (.h) and implement its methods in a cpp file (.cpp), but it does not work.
main.cpp:
#include <iostream>
#include "Message.h"
using namespace std;
int main()
{
Message *t = new (Message);
t->display();
return 0;
}
Message.h:
#ifndef MESSAGE_H_INCLUDED
#define MESSAGE_H_INCLUDED
class Message {
public:
void display();
};
#endif // MESSAGE_H_INCLUDED
Message.cpp:
#include "Message.h"
void Message::display() {
cout << "Hello!";
}
I don't understand why I keep getting the following error
undefined reference to 'Message::display()'
Compile this with the command g++ -std=c++11 Message.cpp main.cpp
I've defined the following header file (in C), left out the function implementation since thise aren't needed:
#ifndef FFMPEG_MEDIAMETADATARETRIEVER_H_
#define FFMPEG_MEDIAMETADATARETRIEVER_H_
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavutil/dict.h>
int setDataSource(AVFormatContext** pFormatCtx, const char* path);
#endif /*FFMPEG_MEDIAMETADATARETRIEVER_H_*/
In C++, I defined my second header file:
#ifndef MEDIAMETADATARETRIEVER_H
#define MEDIAMETADATARETRIEVER_H
using namespace std;
extern "C" {
#include "ffmpeg_mediametadataretriever.h"
}
class MediaMetadataRetriever
{
public:
MediaMetadataRetriever();
~MediaMetadataRetriever();
int setDataSource(const char* dataSourceUrl);
};
#endif // MEDIAMETADATARETRIEVER_H
In, mediametadataretriever.cpp I defined the following function:
int MediaMetadataRetriever::setDataSource(
const char *srcUrl)
{
// should call C function
AVFormatContext* pFormatCtx;
return setDataSource(&pFormatCtx, srcUrl);
}
When I try to compile this (C++) project in Eclipse I get a "No matching function call..." error related to:
return setDataSource(&pFormatCtx, srcUrl);
If I comment out the call, the code compiles fine:
int MediaMetadataRetriever::setDataSource(
const char *srcUrl)
{
return 0;
}
This appears to be a linking issue, does anyone know what I'm doing wrong?
setDataSource in that context is the name of the member function. To invoke the free function, try fully qualifying its name:
return ::setDataSource(&pFormatCtx, srcUrl);
// ^^
just a very small program to test how to use the namespace. I divide it into 3 files, since in large product, ns.h is the namespace interface and ns.cpp is the implementation. I cannot put all these stuff into one file.
Here is the code:
//ns.h
#ifndef MY_H
#define MY_H
namespace my
{
int a=1;
int b=0;
void test();
}
#endif
//ns.cpp
#include <iostream>
#include "ns.h"
using namespace my;
//my::a=1;
//my::b=0;
void my::test()
{
std::cout<<a<<std::endl;
}
//testns.cpp
#include <iostream>
#include "ns.h"
int main()
{
std::cout<<my::b<<std::endl;
my::test();
}
If I keep the above code, and compile will get:
testns.obj : error LNK2005: "int my::b" (?b#my##3HA) already defined in ns.obj
testns.obj : error LNK2005: "int my::a" (?a#my##3HA) already defined in ns.obj
If I comment the statement #include "ns.h" I will get undefined error.
D:\mfc\testns.cpp(5) : error C2653: 'my' : is not a class or namespace name
D:\mfc\testns.cpp(5) : error C2065: 'b' : undeclared identifier
D:\mfc\testns.cpp(6) : error C2653: 'my' : is not a class or namespace name
D:\mfc\testns.cpp(6) : error C2065: 'test' : undeclared identifier
Kindly help me if you know how to do this. Thanks a lot.
Headers are for declarations, not definitions. That's nothing to do with the namespace problem.
//ns.h
#ifndef MY_H
#define MY_H
namespace my
{
extern int a, b; // declared, not defined thanks to 'extern'.
void test();
}
#endif
//ns.cpp
#include <iostream>
#include "ns.h"
int my::a=1; // now we provide the actual definitions.
int my::b=0;
void my::test()
{
std::cout << my::a << std::endl;
}
//testns.cpp
#include <iostream>
#include "ns.h"
int main()
{
std::cout << my::b << std::endl;
my::test();
}
You've defined the two variables a and b in ns.h and then the header file is being included in two source files. This violates the one definition rule as the variables are now defined in both the translation units that are including ns.h.
What you need to do is declare variables in the header and define them in a single source file.
To fix the problem, change ns.h to
#ifndef MY_H
#define MY_H
namespace my
{
extern int a;
extern int b;
void test();
}
#endif
In ns.cpp
#include <iostream>
#include "ns.h"
using namespace my;
int my::a=1;
int my::b=0;
void my::test()
{
std::cout<<a<<std::endl;
}
It's not standard practice to define variables in a header file; they are re-defined every time you #include the header, leading to the linker errors that you are seeing.
If you need to share variables between source files (and there's very few good reasons for this), then you should declare them as extern in the header file, and then define them in one of your source files.