Correct.
If a header does not even contain the name of another class - even if its corresponding .cpp file does - then it does not need any reference to it. The cpp file can take care of its own requirements.
If a header uses the name of another class and nothing further, you can usually get away with a "class OtherClass;" declaration.
If a header is using another class fully - e.g. you've got inline functions in your header that call the other class's methods - then you need a full #include "otherClass.h" directive.
If you can get away with no reference or a simple class declaration, you should - not just because it avoids circular dependencies, but because it reduces build times.
simple OOP Linker error help
Author
I've got this code now..
init.h
init.cpp
main.cpp
The problem is, if I don't #include <string> in main, I get a bunch of errors. My question is, why is this happening? I have included string in init.cpp and main doesn't use it..
Those are the errors I'm getting:
<code>
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2653: 'std' : is not a class or namespace name
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2065: 'string' : undeclared identifier
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2146: syntax error : missing ')' before identifier 'filename'
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2059: syntax error : ')'
</code>
init.h
#ifndef INIT_H#define INIT_Hbool init(); // initialize SDL subsystems and TTFSDL_Surface* loadImage( std::string filename ); //the image loading function//apply a surface on the screenvoid applySurface( int x, int y, SDL_Surface* source, SDL_Surface* destination = SDL_GetVideoSurface() );#endifinit.cpp
#include "SDL/SDL.h"#include "SDL/SDL_image.h"#include "SDL/SDL_ttf.h"#include <string>#include "init.h"bool init(){ //initialize SDL subsystems if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 ) { fprintf( stderr, "SDL could not be initialized.\n" ); return false; } else atexit( SDL_Quit ); if( TTF_Init() == -1 ) { fprintf( stderr, "TTF could not be initialized.\n" ); return false; } else atexit( TTF_Quit ); return true;}SDL_Surface* loadImage( std::string filename ){ SDL_Surface* loadedImage = NULL; SDL_Surface* optimizedImage = NULL; loadedImage = IMG_Load( filename.c_str() ); if( loadedImage != NULL ) { optimizedImage = SDL_DisplayFormat( loadedImage ); SDL_FreeSurface( loadedImage ); } else fprintf( stderr, "Image could not be loaded.\n" ); if( optimizedImage != NULL) { //map the color key, turquoise Uint32 colorkey = SDL_MapRGB( optimizedImage->format, 0, 0xFF, 0xFF ); SDL_SetColorKey( optimizedImage, SDL_SRCCOLORKEY, colorkey ); } return optimizedImage;}void applySurface( int x, int y, SDL_Surface* source, SDL_Surface* destination ){ SDL_Rect offset; offset.x = x; offset.y = y; SDL_BlitSurface( source, NULL, destination, &offset );}main.cpp
#include "SDL/SDL.h"//#include <string> ERROR#include "init.h"const int SCREEN_WIDTH = 640;const int SCREEN_HEIGHT = 480;const int BPP = 32;int main( int argc, char* args[] ){ if( !init() ) return 0; return 0;}The problem is, if I don't #include <string> in main, I get a bunch of errors. My question is, why is this happening? I have included string in init.cpp and main doesn't use it..
Those are the errors I'm getting:
<code>
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2653: 'std' : is not a class or namespace name
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2065: 'string' : undeclared identifier
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2146: syntax error : missing ')' before identifier 'filename'
1>f:\my documents\visual studio 2005\projects\blocks\blocks\init.h(5) : error C2059: syntax error : ')'
</code>
Author
Quote:Original post by oler1s
Take a look at your init.h file. You use std::string. But where's <string>?
In init.cpp :-/
Quote:Original post by sheep19Yes it does. It includes init.h, which uses it.
and main doesn't use it..
There is absolutely zero connection between a .h and .cpp file that both have the same name. None. It's purely a coding convention that you keep them in pairs. What init.cpp may or may not have in it has no effect on init.h.
Either you should put a forward declaration for std::string in the header - something like "class std::string;" - or you should put the include there instead of in the CPP files.
This topic is closed to new replies.
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