How to introduce values in an array of structs? (c++)

Question

I want to make a program that lets the user input the brand, price and color of a car for an unknown amount of cars, and cant figure out how to do that or what i have to search for in order to understand.

Example of what i want it to do: i want 20 cars, and i want to input values for each one of them and at the end have the program say which brand is the most expensive.

#include <iostream>

using namespace std;

struct car{

    char brand[50];
    char color[60];
    unsigned short int price;

};

void compare(car a, car b){
    if(a.price > b.price)
        cout << "Most expensive: " << a.brand;
    else
        cout << "Most expensive: " << b.brand;
}

int main()
{
    car m1, m2;
    cout << "Brand of first car: "; cin >> m1.brand; cout << endl;
    cout << "Color of first car: "; cin >> m1.color; cout << endl;
    cout << "Price of first car: "; cin >> m1.price; cout << endl << endl;

    cout << "Brand of second car: "; cin >> m2.brand; cout << endl;
    cout << "Color of second car: "; cin >> m2.color; cout << endl;
    cout << "Price of second car: "; cin >> m2.price; cout << endl << endl;

    compare(m1, m2);

    return 0;
}

Since you tagged as C++, prefer to use `std::string` for text instead of character arrays. Character arrays can overflow and **you** have to manage the memory. The `std::string` manages memory for you, expanding as necessary. — Thomas Matthews, May 12 '21 at 17:07

score 1 · Accepted Answer · answered May 12 '21 at 16:58

1

Your first step will be:

int main()
{
    car m[20]; // todo better: std::vector

    for(int i=0; i < 20; i++)
    {
        cout << "Brand of first car: "; cin >> m[i].brand; cout << endl;
        cout << "Color of first car: "; cin >> m[i].color; cout << endl;
        cout << "Price of first car: "; cin >> m[i].price; cout << endl << endl;
    }
}

The next step will be to do something with m[].

answered May 12 '21 at 16:58

Jeffrey

11,063
1
21
42

`C++` has a string type. Use it. Not using it will end in tears. – Mark Roberts May 12 '21 at 16:58
yeah. Trying to stick with the user's existing code – Jeffrey May 12 '21 at 16:59
what does std::vector do exactly? – MickeyMoise May 12 '21 at 17:00
@MarkRoberts It will also end more acquired knowledge (given enough perseverance) which is a good thing. – pfabri May 12 '21 at 17:02
IMHO, a better process is to overload `operator>>` inside the `car` structure. This will encapsulate the data and make reading simpler. – Thomas Matthews May 12 '21 at 17:09
@Jeffrey how do i make the compare function work now? – MickeyMoise May 12 '21 at 17:10
Rather than a compare function, you can overload the `<` operator for `car`. Information on [how to do that (and much other wisdom) here](https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading). – user4581301 May 12 '21 at 17:15

score -1 · Answer 2 · answered May 12 '21 at 17:01

-1

If you create your object (of type car) named m1, m2 and then you would like to add some values to its' fields, you have to create the object dynamically, so it will be:

car *m1 = new car;
cin >> m1->brand;

I'm more into Java right now, so I'm not 100% sure about the syntax, but the concept seems right. Hope it works! ;-)

answered May 12 '21 at 17:01

The_Long_Distance_Runner

495
6
17

Anyway arrays of char might cause troubles, so as others said, it's better to use String insted ;-) – The_Long_Distance_Runner May 12 '21 at 17:04
1

there is no need to use `new` here, or any dynamic allocation. – 463035818_is_not_an_ai May 12 '21 at 17:05
why? so how to add values to fields while the program is running? – The_Long_Distance_Runner May 12 '21 at 17:06
1

`car m1; cin >> m1.brand;` if that doesnt work then your code doesnt work as well. – 463035818_is_not_an_ai May 12 '21 at 17:07
Please note that Java and C++ are fundamentally different. While `new` is the way to create objects in Java, in C++ it isnt. – 463035818_is_not_an_ai May 12 '21 at 17:10
1

I mean you can do it, but you also dont juggle with chainsaws while performing a headstand, just because it is possible in principle – 463035818_is_not_an_ai May 12 '21 at 17:12
(i was exaggerating a bit, to get the point across, but seriously `new` is to be avoided in modern C++) – 463035818_is_not_an_ai May 12 '21 at 17:13

How to introduce values in an array of structs? (c++)

2 Answers2