c++ combine singleton and visitor pattern

I'm having a problem with pointers. My background is Java and I've still not got the hand of using pointers. My error is:

syntax error: identifier 'StockController'

from this line:

virtual void visit(StockController* stock) = 0;

I've implemented my singleton. But now i'm looking to add the visitor pattern. I have a series of operations ill be applying to the collection of objects.

Visitor abstract class:

#ifndef VISITOR_H
#define VISITOR_H

#include "StockController.h"

class Visitor
{
public:
    virtual void visit(StockController* stock) = 0;
};

#endif

Singleton class:

#ifndef StockController_H
#define StockController_H

#include <iostream>
#include "Visitable.h"

using namespace std;

class StockController : public Visitable {
public:
    /*Returns an instance of the class */
    static StockController* getInstance();

protected:
    /* Prevent initialisation unless through get method */
    StockController();
    StockController(const StockController&);
    StockController& operator= (const StockController&);

private:

    /* Class instance */
    static StockController* _instance;

};

#endif

Visitable.h:

#ifndef VISITABLE_H
#define VISITABLE_H

#include "Visitor.h"

class Visitable {
public:
    virtual void accept(Visitor &visitor) = 0;

};

#endif