c ++ struct 未命名类型

I am defining a structure in a header file, and then setting its members in the corrosponding .cpp file. For doing this I am using a function that is supposed to create a (same) structure in its scope, and then return it. Something like this:

在标题中:

#include <things>
class GLWindow : public QGLWidget, public QGLFunctions
{
    Q_OBJECT
public:
    GLWindow(QWidget *parent = 0);
    ~GLWindow();

    //....
    struct Drawable
    {
        GLuint     vertexBuffer;
        GLuint     indexBuffer;
        int        faceCount;
        QMatrix4x4 transform;
    }cube;
    GLuint cubeTex;

    Drawable CreateDrawable(GLfloat* C_vertices, GLfloat* C_tex, GLfloat* C_normals, GLushort* C_facedata, int faces);
    //.....
};

在 cpp 文件中:

#include "glwindow.h"

Drawable GLWindow :: CreateDrawable(GLfloat *C_vertices, GLfloat *C_tex, GLfloat *C_normals, GLushort *C_facedata, int faces)
{
    int faceCount =faces;

    QMatrix4x4 Transform;
    Transform.setToIdentity();

    GLuint VB;
    /*Create vertexbuffer...*/

    GLuint IB;
    /*Create indexbuffer...*/

    Drawable drawable;
    drawable.faceCount = fCount;
    drawable.transform = Transform;
    drawable.vertexBuffer = VB;
    drawable.indexBuffer = IB;

    return drawable;
}

void GLWindow :: someOtherFunction()
{
    //.....
    cube = CreateDrawable(cube_vertices, cube_tex, cube_normals, cube_facedata, cube_face);
    //.....
}

我收到一个错误，指出 'Drawable' 没有命名类型，但我不明白为什么我会收到这个错误，或者我可以做些什么来消除它.>

GLWindow::Drawable GLWindow :: CreateDrawable(GLfloat *C_vertices, GLfloat *C_tex, GLfloat *C_normals, GLushort *C_facedata, int faces)