I am learning OOP in C++, and I am writing the most basic class. I am having a problem with declaring an object for the class. I getting the error posted in the title. I know my class works because I put the class in “main.cpp”, and I could declare an object no problem. Why is this happening? How can I fix it?

My code

Food.h

#ifndef PORJECT2_FOOD_H
#define PORJECT2_FOOD_H

const char* RecommendFood(char firstLetter);
class Foods;

#endif //PORJECT2_FOOD_H

Food.cpp

#include "Food.h"
#include <String>
using namespace std;

class Foods{
public:
    string name;
    int qty;

    const string &getName() const {
        return name;
    }

    void setName(const string &name) {
        Foods::name = name;
    }

    int getQty() const {
        return qty;
    }

    void setQty(int qty) {
        Foods::qty = qty;
    }
};

main.cpp

    Foods obj;
    string food1 = "Fruit", food2 = "Veggies", Food1, Food2;
    int qty1 = 15, qty2 = 165, QTY1, QTY2;

    obj.setName(food1);
    obj.setQty(qty1);
    Food1 = obj.getName();
    QTY1 = obj.getQty();
    cout << "Food: " << Food1 << " Qty: " << QTY1 << "n";

    obj.setName(food2);
    obj.setQty(qty2);
    Food2 = obj.getName();
    QTY2 = obj.getQty();
    cout << "Food: " << Food2 << " Qty: " << QTY2 << "n";

    return 0;
}