C ++ lnk error 2019 unresolved external characters virtual errors due to interface ... (?)

Question

I'm having problems creating a good interface and using it ... My review of settings:

"interface" GraphicsLibrary.H ...

virtual void drawPoint(const Point& p, unsigned char r, unsigned char g, unsigned char b, double pointSize); 

with the empty GraphicsLibrary.ccp! because its interface, so "OpenGL" is a graphics library ... so I have OpenGL.CPP with:

 void GraphicsLibrary::drawPoint(const Point& p, unsigned char r, unsigned char g, unsigned char b, double pointSize) { //some code } 

which, of course, is "empty" by OpenGL.h (since its header file is GraphicsLibrary.h)

then I have a class with more specific functions that OpenGL uses and uses these basic drawing functions ... ( OpenGLVis_Enviroment.cpp ):

 OpenGL ogl; void drawObstacleUnderConstruction(Obstacle::Type type, const vector<Point>& points) { for( //etcetc ) ogl.drawPoint(*it, 255, 255, 255, 3.0); } 

BUT I also have a main function using some OpenGL functions ... so main also:

 OpenGL openGL; openGL.drawText(something); 

but now I have many such errors (I have the same with all other functions):

 1>OpenGLVis_Environment.obj : error LNK2019: unresolved external symbol "public: virtual void __thiscall GraphicsLibrary::drawPoint(struct Point const &,unsigned char,unsigned char,unsigned char,double)" ( ?drawPoint@GraphicsLibrary @@ UAEXABUPoint@ @ EEEN@Z ) referenced in function "void __cdecl DrawingFunctions::drawObstacleUnderConstruction(enum Obstacle::Type,class std::vector<struct Point,class std::allocator<struct Point> > const &)" ( ?drawObstacleUnderConstruction@DrawingFunctions @@ YAXW4Type@Obstacle @@ ABV?$vector@UPoint @@ V?$allocator@UPoint @@@ std@ @@ std@ @@Z) 

Is it because I use "GraphicsLibrary :: drawPoint ..."? I’ve been searching the Internet for ages, but it's hard to find many examples of interfaces .. and how to work with them ... Thanks in advance guys

Answer 1

The component complains about DrawingFunctions::drawObstacleUnderConstruction , and you have defined void drawObstacleUnderConstruction , which is a free feature.

Define a name when defining a function.

 void DrawingFunctions::drawObstacleUnderConstruction(Obstacle::Type type, const vector<Point>& points) { for( //etcetc ) ogl.drawPoint(*it, 255, 255, 255, 3.0); }