How to use vector to modify a struct c++

Question

Hey guys this code is for a coffee machine. I am trying to add a operator mode for this machine.

#include <iostream>
#include <string>
#include <iomanip>

using namespace std;

struct coffee {
  string name;
  int itemprice;
  string country;
  int quantity;

};

float remainder, price2, price;
int main() {
      int coffeetype = 1; 
    cout<<"\nPress'1'for buy a coffee\n";
    cout<<"\nPress' 2' for operator mode\n\n";
    int input;
    cin>>input;
    if (input==2)
    {
        cout << "Welcome to operator mode \n";
        cout << "Press '1' for add more coffee powder \n";
        cout << "Press '2' for exit\n";
        int op;
        cin >> op;
        if(op==2){
            return op;
        }
    }
        coffee drink[] = {
      { "Espresso", 120, "Italy", 20 },
      { "Iced coffee", 150, "France", 20 },
      { "Long black", 80, "Austral", 20 },
      { "Americano", 100, "America", 20 },
      { "Latte", 200, "Italy", 20 },
      { "Irishcoffee",130, "Ireland", 20 },
      { "Cappuccino", 180, "Italy", 20 }
    };

        cout << fixed;
        cout << setprecision(2);

   cout<<"Enter the name of coffee";



    while(coffeetype != 8){
    for (int i = 0; i != sizeof(drink)/sizeof(drink[0]); ++i)
        cout<< "\n " << i+1 << ") "<<drink[i].name<<"\t\t"<<drink[i].itemprice<<"\t\t"<<drink[i].country<<"\t\t("<<drink[i].quantity<<") remaining";

I've used a vector for this struct part.

vector<coffee> drink {
    { "Espresso", 120, "Italy", 20 },
    { "Iced coffee", 150, "France", 20 },
    { "Long black", 80, "Austral", 20 },
    { "Americano", 100, "America", 20 },
    { "Latte", 200, "Italy", 20 },
    { "Irishcoffee",130, "Ireland", 20 },
    { "Cappuccino", 180, "Italy", 20 }
};

but after using this part my 'for loop' didn't work.. Could some one help me to 'cout' the vector part.

And also i need your help to make the operator mode.By operator mode operator should be able to add more coffee types and change the number of coffees in the machine..Below i have shown the code i got from one of the contributor in stackoverflow.But i dont know how to implement below code part to my code.

coffee entry;
cin >> entry.country
    >> entry.itemprice
    >> entry.country
    >> entry.quantity;
drink.push_back(entry);

How to use above code to modify details in the struct(drink).

Answer 1

First, drink is a poor choice of name for the array, which holds information regarding many dirnks - and in fact, many coffee-based drinks. So let's call it coffee_drinks .

The problem with your for loop is probably your use of:

sizeof(drink)/sizeof(drink[0])

this "hack" works for C-style arrays - not for std::vector s. The sizeof() an std::vector is not the total size in bytes of its elements - since the memory of the elements is dynamically allocated on the heap, and is only pointed to by the vector class instance.

You could just write:

for(int i = 0; i < coffee_drinks.size(); i++)

but even better, you can make it:

for(coffee drink : coffee_drinks)

which iterates over all elements in the std::vector . This "trick" works for any class which has a begin() and end() member; it's called a range-based for loop .