Inheritance problem

[Steven Schveighoffer]

On Fri, 11 Feb 2011 15:40:18 -0500, %u <unknown at unknown.com> wrote:

> Hello,
>
> I've a problem with my class inheritance. I have class called Texture
> which implements the interface IDrawable and the abstract class
> APickable.
> The Texture-class contains 3 members which looks like this:
>
> GLuint pTextureID;
>
> Size pSize1, pSize2;
>
> Finally... my Texture-class looks like:
>
> class Texture : APickable, IDrawable {
>    protected {
>       GLuint pTextureID;
>       Size pSize, pAnoutherSize;
>    }
> }
>
> now... I have a second class called Animation which looks like this:
>
> class Animation : Texture {
>    private {
>       Texture[] pFrames;
>    }
>    public {
>       this(string file, string[] paths...) {
>          super(file);
>          pFrames ~= this;
>          foreach(string cur; paths) {
>             pFrames ~= new Texture(cur);
>          }
>       }
>
>       Size getSize() {
>          return pFrames[0].pSize;
>       }
>    }
> }
>
> As I know, pFrames[0].pSize can be called... pSize in the Texture-
> class is marked as protected, but I get the following error:
>
> Error: class Texture member pSize is not accessible.
>
> When I mark the protected members of the Texture-class as public, it
> works (should be clear), but why do I get this error when mark them
> as protected?
>
> I hope anyone can help to solve the problem.

protected means you cannot access it outside the *instance*.  The pFrames  
array references *other instances* of Texture, so they are not accessible.

http://www.digitalmars.com/d/2.0/attribute.html#ProtectionAttribute

"If accessing a protected instance member through a derived class member  
function, that member can only be accessed for the object instance which  
is the ‘this’ object for the member function call."

-Steve