How to create a user-defined amount of objects?

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I am creating a Bookshop and at the time of registering a new book, the user must say the amount of books that will be registered, but I am not able to do it, I can only create a preset amount of object.

Here in the code I tried to create an array, but it requires that it be a constant prevented the user from defining the amount that will be created.

void AddNewBook() {
    system("CLS");

    int amountBooks;

    std::cout << "How many books will be added? ";
    std::cin >> amountBooks;

    if (amountBooks < 1) {
         Error("No book will be added.");
         Options(Choice());
    }
    else {
        Book books[amountBooks];
    }
}

I wonder if there is a way to create the amount of objects that the user needs dynamically?

I beg your pardon if my doubt is not clear.

c++

  • I think this can help you: https://stackoverflow.com/questions/44678457/dynamic-objects-in-c/44678941#:~:text=If%20you%20write%20A%20*%20a,A%20and%20not%20an%20array. and also: https://answall.com/questions/87980/forms

1 answer

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Cannot create statically allocated array using a non-constant size (not known at compile time).

Correct means of declaring an array:

char array[5];

const size_t amount = 10;
char array[amount];

#define amount 15;
char array[amount];

static constexpr size_t amount = 20;
char array[amount];

To create an array that has a dynamic size, just use one of the Std library templates, the vector:

#include <vector>
std::vector<Book> books;
Book book;
books.push_back(book);

Is used push_back() to add elements to the vector and operator [] to access them just like in an array. It is not necessary to specify a size at boot time, but to decrease the amount of allocations (and increase performance), you can use reserve() to preset the size of vector.

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