Question

hi im trying to pass some values to a class but it wont let me it says invalid use of class ‘Figure’ im trying to send 3 values x,y,z and thats all but it wont let me heres what im trying to do…

here is the main.cpp and the function that calls the class Figure

 for (j = 0; j < num_elems; j++) {
    /* grab and element from the file */
    vlist[j] = (Vertex *) malloc (sizeof (Vertex));
    ply_get_element (ply, (void *) vlist[j]);


    int vert=sprintf(szFile,"vertex: %g %g %g", vlist[j]->x, vlist[j]->y, vlist[j]->z);
    /* print out vertex x,y,z for debugging */
    TextOut(hDC,600,j*20,szFile,vert);
   DrawFig->Figure(vlist[j]->x, vlist[j]->y, vlist[j]->z);
  }

The error is here

   DrawFig->Figure(vlist[j]->x, vlist[j]->y, vlist[j]->z);
  }

Here is the WM_CREATE: where i initialize everything

case WM_CREATE:
        hDC = GetDC(hWnd);
     //ShowWindow(g_hwndDlg,SW_SHOW);
    hRC=wglCreateContext(hDC);
    wglMakeCurrent(hDC,hRC);
     g_hwndDlg = CreateDialog(hInst,MAKEINTRESOURCE(IDD_DIALOG1),hWnd,DialogProc);

    DrawFig= new Figure(1.0,1.0,1.0);
    initGL();
     break;

here is the Figure.h

class Figure
{
    public:
        Figure(float x,float y,float z);
        void Draw();
        float paramx(){
        return x1;
        }
        float paramy(){
        return y1;
        }
        float paramz(){
        return z1;
        }
    protected:
    private:
    float x1,y1,z1;
    list <Figure> m_vertices;
};

and here is the Figure.cpp

Figure::Figure(float x,float y,float z){
    this->x1=x;
this->y1=y;
this->z1=z;
m_vertices.push_back(Figure(x1, y1, z1));
}

void Figure::Draw()
{
    list<Figure>::iterator p = m_vertices.begin();
 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    gluLookAt(0.0,0.0,4.0,0.0,0.0,0.0,0.0,1.0,0.0);

    glColor3f(0.7f,1.0f,0.3f);
    glBegin(GL_LINE_LOOP);
    while(p != m_vertices.end()){
        glNormal3f(p->paramx(),p->paramy(),p->paramz());
        glVertex3f(p->paramx(),p->paramy(),p->paramz());
        p++;
    }
    glEnd();
}

any ideas? this is opengl,c++ and im using codeblocks 10.05 just in case
oh yeah im initializing it at the main.h like this DrawFig* Figure;

Answer 1

@dark_charlie’s answer is almost correct. Here is a better version that will actually work, but still probably isn’t what you want:

class Figure  {
  // ...
public:
  void set(float x, float y, float z);
  // ...
};

void Figure::set(float x, float y, float z)
{
  // Your original code from the constructor
  this->x1 = x;
  this->y1 = y;
  this->z1 = z;
}

Figure::Figure(float x, float y, float z)
{
  // In the constructor call the newly created set function
  set(x, y, z);
  m_vertices.push_back(Figure(x1, y1, z1));
}


// Replace the faulty line with this:
DrawFig->set(vlist[j]->x, vlist[j]->y, vlist[j]->z);

Now, this is almost certainly not what you want. But it’s also really hard to figure out what you do want. You have a design problem. The design problem is that Figure has two responsibilities. It is both a point in space, and a set of points describing a figure. This confusion of responsibilities is leading your class to not actually be able to fill either of them particularly well.

You need two classes. You need a Point class and a Figure class. The Figure class should allow you to set the location of the figure as well as letting you add points to the figure’s outline.

The huge clue that something is wrong is this list<Figure> m_vertices;. It’s very rare that a class conceptually contains instances of itself. And usually when you do it you’re building your own data structure like a tree or a list and then the class contains pointers to instances of itself.

Also, the fact that @dark_charlie’s simple fix resulted in infinite recursion is another huge clue that something is wrong.

I’m guessing this is a homework assignment, so this is all the help I will give you aside from telling you that I think you already have a Point class that you call Vertex.