Class does not persist vector of objects after addition

Question

My code is as shown below. The problem is inside the int main() function, r.printItems() is not printing anything. What am I missing here?

main.cpp

#include <bits/stdc++.h>
#include "Customer.h"
#include "MenuCreator.h"
#include "FoodItem.h"

MenuCreator m1;

void createCustomer() {
    Customer c1("mrg", "m@gmail.com", "9654357", "+91");
}

void createRestaurantItem(Restaurant &rest) {
    rest.addItems(FoodItem("t1"));
    rest.addItems(FoodItem("D1"));
}

void createMenu() {
    m1.createMenu("sg");
    Category c1;
    c1.setName("Non-veg");
    m1.addCategory(c1);
    Restaurant r1;
    r1.setName("ABC");
    r1.setDescription("Test Restaurant");
    createRestaurantItem(r1);
    c1.addRestaurants(r1);
}

vector<Restaurant> getRestaurantsForCategory(string category) {
    return m1.getRestaurantsForCategories(category);
}


int main() {
    createCustomer();
    createMenu();
    for (auto r: getRestaurantsForCategory("Non-veg")) {
        r.printItems();
    }
    return 0;
}

MenuCreator.h

#include <bits/stdc++.h>
#include "Menu.h"

using namespace std;

class MenuCreator {

public:

    void createMenu(string name) {
        Menu m1;
        m1.setName(name);
        menu = m1;
    }

    void addCategory(const Category &categ) {
        categories.push_back(categ);
    }

    const Menu &getMenu() const {
        return menu;
    }

    const vector<Category> &getCategories() const {
        return categories;
    }

    void addRestaurantForCategory(string name, const Restaurant restaurant) {
        for(auto categ: categories) {
            if (categ.getName() == name) {
                categ.addRestaurants(restaurant);
            }
        }
    }

    const vector<Restaurant> &getRestaurantsForCategories(string category) {
        for(auto categ: categories) {
            if(categ.getName() == category) return categ.getRestaurants();
        }
    }

private:
    Menu menu;
    vector<Category> categories;
};

Menu.h

#include<bits/stdc++.h>
#include "Category.h"

using namespace std;

class Menu {
public:
    const string &getName() const {
        return name;
    }

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

private:
    string name;
    string description;
    vector<Category> categories;
};

Category.h

using namespace std;

class Category {
public:
    const string &getName() const {
        return name;
    }

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

    const string &getDescription() const {
        return description;
    }

    void setDescription(const string &description) {
        Category::description = description;
    }

    const vector<Restaurant> &getRestaurants() const {
        return restaurants;
    }

    void setRestaurants(const vector<Restaurant> &restaurants) {
        Category::restaurants = restaurants;
    }

    void addRestaurants(const Restaurant &rt) {
        Category::restaurants.push_back(rt);
    }

private:
    string name;
    string description;
    vector<Restaurant> restaurants;
};

FoodItem.h

#include <bits/stdc++.h>
#include <vector>
#include "FoodItem.h"

using namespace std;

class Restaurant {
public:

    Restaurant() {
        this->id = gen_random(12);
    }

    virtual ~Restaurant() {

    }

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

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

    const string &getDescription() const {
        return description;
    }

    void setDescription(const string &description) {
        Restaurant::description = description;
    }

    double getLat() const {
        return lat;
    }

    void setLat(double lat) {
        Restaurant::lat = lat;
    }

    double getLang() const {
        return lang;
    }

    void setLang(double lang) {
        Restaurant::lang = lang;
    }

    const string &getImageUrl() const {
        return imageUrl;
    }

    void setImageUrl(const string &imageUrl) {
        Restaurant::imageUrl = imageUrl;
    }

    const string &getVideoUrl() const {
        return videoUrl;
    }

    void setVideoUrl(const string &videoUrl) {
        Restaurant::videoUrl = videoUrl;
    }

    const vector<FoodItem> &getItems() const {
        return items;
    }

    void setItems(const vector<FoodItem> &items) {
        Restaurant::items = items;
    }

    void addItems(const FoodItem &item) {
        this->items.push_back(item);
    }

    string gen_random(const int len) {
        string tmp_s;
        static const char alphanum[] =
                "0123456789"
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                "abcdefghijklmnopqrstuvwxyz";
        srand( (unsigned) time(NULL) * getpid());
        tmp_s.reserve(len);
        for (int i = 0; i < len; ++i)
            tmp_s += alphanum[rand() % (sizeof(alphanum) - 1)];
        return tmp_s;

    }

    const string &getId() const {
        return id;
    }

    void printItems() {
        for(auto it: items) {
            cout<<"item: "<<it.getName()<<endl;
        }
    }


private:
    string id;
    string name;
    string description;
    double lat;
    double lang;
    string imageUrl;
    string videoUrl;
    string createdAt;
    string updatedAt;
    vector<FoodItem> items;
};

Restaurant.h

#include <bits/stdc++.h>
#include <vector>
#include "FoodItem.h"

using namespace std;

class Restaurant {
public:

    Restaurant() {
        this->id = gen_random(12);
    }

    virtual ~Restaurant() {

    }

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

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

    const string &getDescription() const {
        return description;
    }

    void setDescription(const string &description) {
        Restaurant::description = description;
    }

    double getLat() const {
        return lat;
    }

    void setLat(double lat) {
        Restaurant::lat = lat;
    }

    double getLang() const {
        return lang;
    }

    void setLang(double lang) {
        Restaurant::lang = lang;
    }

    const string &getImageUrl() const {
        return imageUrl;
    }

    void setImageUrl(const string &imageUrl) {
        Restaurant::imageUrl = imageUrl;
    }

    const string &getVideoUrl() const {
        return videoUrl;
    }

    void setVideoUrl(const string &videoUrl) {
        Restaurant::videoUrl = videoUrl;
    }

    const vector<FoodItem> &getItems() const {
        return items;
    }

    void setItems(const vector<FoodItem> &items) {
        Restaurant::items = items;
    }

    void addItems(const FoodItem &item) {
        this->items.push_back(item);
    }

    string gen_random(const int len) {
        string tmp_s;
        static const char alphanum[] =
                "0123456789"
                "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                "abcdefghijklmnopqrstuvwxyz";
        srand( (unsigned) time(NULL) * getpid());
        tmp_s.reserve(len);
        for (int i = 0; i < len; ++i)
            tmp_s += alphanum[rand() % (sizeof(alphanum) - 1)];
        return tmp_s;

    }

    const string &getId() const {
        return id;
    }

    void printItems() {
        for(auto it: items) {
            cout<<"item: "<<it.getName()<<endl;
        }
    }


private:
    string id;
    string name;
    string description;
    double lat;
    double lang;
    string imageUrl;
    string videoUrl;
    string createdAt;
    string updatedAt;
    vector<FoodItem> items;
};

Have you tried using a debugger? Please provide a [mre] (with a focus on minimal) and explain what your code is supposed to do — Alan Birtles, Mar 27 '21 at 17:44
yes, @OznOg debugged the code FoodItem list inside Restaurant is empty when I am getting it via MenuCreator file — Mrugesh, Mar 27 '21 at 17:52
There's quite a bit of room for improvement in your code. [Don't `#include `](https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h), unnecessary use of `this->`, `lang` should be `longitude`, [avoid `std::endl`](https://stackoverflow.com/questions/213907/stdendl-vs-n), in `gen_random()` you should call `resize()` instead of `reserve()`, and so on. Once you get a working program, consider posting it on [Code Review](https://codereview.stackexchange.com/). — G. Sliepen, Mar 27 '21 at 18:37
In `createMenu`, you call `c1.addRestaurants` after `m1.addCategory(c1)`. The copy of `c1` stored in `m1` doesn't have any restaurants in it. — Igor Tandetnik, Mar 28 '21 at 00:32

Remy Lebeau · Accepted Answer · 2021-03-28T18:36:23.833

When createMenu() in main.cpp is setting up the menu, it creates a local Category object named c1 and adds it to the menu, which makes a copy of c1 when pushingnit into the MenuCreator::categories vector. No Restaurant objects had been added to c1 yet when that copy is created. So when a Restaurant is then added to c1 afterwards, the copy is not updated. That is why there are no Restaurant objects in the menu when MenuCreator::getRestaurantsForCategory() tries to return them.

Change createMenu() to fully initialize c1 before adding it to the menu, eg:

void createMenu() {
    m1.createMenu("sg");
    Category c1;
    c1.setName("Non-veg");
    Restaurant r1;
    r1.setName("ABC");
    r1.setDescription("Test Restaurant");
    createRestaurantItem(r1);
    c1.addRestaurants(r1);
    m1.addCategory(c1); // <-- move down here
}

Also, on a side note, the return value of MenuCreator::getRestaurantsForCategories() is undefined if the specified category is not found. Since the return value is a reference to a vector, it needs to either return a static vector that is empty, or else throw an exception.

is there any way to pass it by reference so that I don't have to maintain the order in which it was added? — Mrugesh, Mar 28 '21 at 18:24
@MrugeshThaker you can't store references in `std::vector` (unless you use `std::reference_wrapper`, but you risk dangling references when objects go out of scope). You can store pointers, which means using dynamic allocations with `new`/`std::unique_ptr`. Otherwise, you may need a redesign. For instance, have `MenuCreator::addCategory()`, `MenuCreator::addRestaurantForCategory()`, `Category::addRestaurants()`, `Restaurant::addItems()`, etc not take an object as input, but instead create and store an object internally, and then return a reference to it for the caller to fill in as needed. — Remy Lebeau, Mar 28 '21 at 18:34

Class does not persist vector of objects after addition

1 Answers1