C ++头函数

Question

Sorry for asking a beginners question. I'm quiet familiar with Java, C# ... but I have to write an OpenGL Program in C++ and there is something I don't understand:

I have to parse a text file to get vertices and put them into a vector. So I wrote a method that receives my vector of Vertex objects. It works when I define the method before I call it

std::vector<AESParser::Vertex> vertices;

void parseVertices(std::vector<AESParser::Vertex> &verts){
 ...
}

...

parseVertices(vertices);

But fails when doing it the other way around. So I understand I have to declare it in the header file. So I wrote something like this:

*** Header ***
class AESParser
{
    public:
        struct Vertex{
            float x;
            float y;
            float z;
        };
        AESParser();
        virtual ~AESParser();
        void read();
    protected:
    private:
        int readNumVertices(std::fstream &stream);
        int readNumFaces(std::fstream &stream);   
        void parseVertices(std::vector<Vertex> &verts);
        Vertex readVertex(std::fstream &stream);  
};

I know there are probably many more mistakes since I never did C++ but the main problem with this is, that I get the following error message:

undefined reference to `AESParser::parseVertices(std::vector<AESParser::Vertex, std::allocator<AESParser::Vertex> >&)'

So something seems to be wrong with the "parseVertices()" method and I don't see what. It works for the others like "readNumVertices()".

Thanks for your help!

Answer 1

Your function belongs to the AESParser class, so you need to define it as such

void AESParser::parseVertices(std::vector<AESParser::Vertex> &verts){
    ...
}

When you have the function definition written as

void parseVertices(std::vector<AESParser::Vertex> &verts)

Then it is a free function (doesn't belong to a class) that happens to have the same name, return the same type, and take the same arguments. But it is a different function.

Note in the first version, there is a AESParser:: scope appended to the front of the function name.