error:a nonstatic member reference must be relative to a specific object

Question

I don't understand why view gives me the error of a nonstatic member reference must be relative to a specific object.

CDrawView::Shape is an enum that i have declared on my CDrawView

enum shape{line, rect, elli};
shape current_shape;

This is my other class

class Shapemaker
{
public:

    CDrawView view;
    static void Create(CDrawView::shape )
    {
        if(view.current_shape == view.line)
        {
            view.m_shape.reset(new Line());
        }
        else if(view.current_shape == view.rect)
        {
            view.m_shape.reset(new Rect());
        }
    }
}

What's the best practice to avoid this error

Solution 1

First of all, since the function is static, it doesn't have access to view. That's because view is a non-static member of Shapemaker, so is only associated with specific instances o Shapemaker. Either view needs to be static or the Create function shouldn't be. The other alternative is that view shouldn't be a member and should be created inside the Create function.

Also, the enum constants' names are within the scope of the CDrawView class and are accessed through the class name like so:

if(view.current_shape == CDrawView::line)

The . operator is for accessing a non-static member of an object. view does not have a non-static member called line or rect.

Solution 2

view is a non-static object of class CDrawView, Create is static function of ShapeMaker class, there will be no instance of view if you do not construct an object of ShapeMaker while Create is not associated with any objects of ShapeMaker. You cannot use nons-tatic members inside a static member function.