Store data in a vector from another class

Question

I have a vector orderQueue that is stored in a class called OrderFood and a function called processUserOption in another class called MerkelMain. I am trying to get processUserOption to store orders in that orderQueue vector using the push_back function. How do I store orders in the orderQueue vector of the OrderFood class?

OrderFood.h

#pragma once
#include <string>
#include <vector>
#include "OrderEntry.h"
#include "CSVReader.h"

class OrderFood
{
    public:
        OrderFood(std::string filename);
        std::vector<OrderEntry> getOrders(OrderType type,
                                          int qty);
    private:
        std::vector<OrderEntry> orderQueue;
};

MerkelMain.cpp

#include <iostream>
#include <vector>
#include "OrderEntry.h"
#include "MerkelMain.h"
#include "OrderFood.h"

MerkelMain::MerkelMain()
{

}

void MerkelMain::init()
{
    std::string input;

    while (true)
    {
        printMenu();    
        input = getUserOption();
        processUserOption(input);
    }
}

void MerkelMain::printMenu()
{
    std::cout << "Welcome to Restaurant Firebird" << std::endl;
    std::cout << "a . Order a plate of chicken rice" << std::endl;
    std::cout << "b . Order a plat for wanton noodles" << std::endl;
    std::cout << "c . Order a cup of Coffee" << std::endl;
    std::cout << "d . Order a cup of Tea" << std::endl;
    std::cout << "e . Repeat Order" << std::endl;
    std::cout << "f . Exit Menu" << std::endl;
    std::cout << "------------------------------------" << std::endl;
    std::cout << "Type an option from a-f" << std::endl;
}


std::string MerkelMain::getUserOption()
{
    std::string choice;
    std::cin >> choice;
    return choice;
}

int MerkelMain::getQuantity()
{
    int qty;
    std::cin >> qty;
    return qty;
}

void MerkelMain::processUserOption(std::string choice)
{
   std::endl(std::cout);

   if (choice == "a")
    {
        std::cout << "How many plates of chicken rice would you like to order?" << std::endl;
        OrderType order = OrderType::chickenrice;
        int qty = getQuantity();
        std::endl(std::cout);
        std::cout << "Thank you for your order of " << qty << " plates of Chicken Rice." << std::endl;
        std::endl(std::cout);
        OrderEntry food_order = OrderEntry(qty, order);
        orderQueue.push_back(food_order)
    }
    if (choice == "b")
    {
        std::cout << "How many plates of wanton noodles would you like to order?" << std::endl;
        OrderType order = OrderType::wantonnoodle;
        int qty = getQuantity();
        std::endl(std::cout);
        std::cout << "Thank you for your order of " << qty << " plates of Wanton Noodles." << std::endl;
        std::endl(std::cout);
        OrderEntry food_order = OrderEntry(qty, order);
        orderQueue.push_back(food_order);
    }
    if (choice == "c")
    {
        std::cout << "How many cups of Coffee would you like to order?" << std::endl;
        OrderType order = OrderType::coffee;
        int qty = getQuantity();
        std::endl(std::cout);
        std::cout << "Thank you for your order of " << qty << " cups of Coffee." << std::endl;
        OrderEntry food_order = OrderEntry(qty, order);
        orderQueue.push_back(food_order);
    }
    if (choice == "d")
    {
        std::cout << "How many cups of Tea would you like to order?" << std::endl;
        OrderType order = OrderType::tea;
        int qty = getQuantity();
        std::endl(std::cout);
        std::cout << "Thank you for your order of " << qty << " cups of Tea." << std::endl;
        std::endl(std::cout);
        OrderEntry food_order = OrderEntry(qty, order);
        orderQueue.push_back(food_order);
    }
    if (choice == "e")
    {
        std::cout << "You have ordered: " << std::endl;

        for (unsigned int i = 0; i < orderQueue.size(); ++i)
        {
            std::cout << orderQueue[i].qty << " " << OrderEntry::orderTypeToString(orderQueue[i].orderType) << std::endl;
        }
        std::endl(std::cout);
    }
    if (choice == "f")
    {
        std::cout << "Thank you and see you again soon." << std::endl;
        
    }
}

Answer 1

You can make class MerkelMain a friend of class OrderFood

class OrderFood
{
    public:
        OrderFood(std::string filename);
        std::vector<OrderEntry> getOrders(OrderType type,
                                          int qty);
    private:
        std::vector<OrderEntry> orderQueue;
        friend class MerkelMain; // <-- HERE
};

then delegate an OrderFood object stored in MerkelMain

class MerkelMain {
    private:
        Orderfood order; // <-- HERE
    ...
};

and then freely invoke the function in MerkelMain methods.

void MerkelMain::processUserOption(std::string choice) {
    ...
    OrderEntry food_order = OrderEntry(qty, order);
    order.orderQueue.push_back(std::move(food_order)); // <-- HERE
    ...
}