如何在C ++中创建参数化对象的数组？

Question

 class book{
private:
    int numOfPages;
public:
    book(int i){
    numOfPages = i;
    };
};

class library{
private:
    book * arrOfBooks;
public:
    library(int x, int y){
        arrOfBooks = new book[x](y);
    };
};
int main()
{
  library(2, 4); 
};

With the example code above I would like to create a library of books that all have the same number of pages. So in the constructor of the library object, whenever a new book is created to be placed in the array I pass the argument in the parenthesis. The above code when tested in C++ shell shows error: "parenthesized initializer in array new". This is for the completion of a school project and no vectors are allowed (as it would be wise to do as I found doing my research) though I cannot think of any other ways to do it than the one shown above...

Answer 1

There is no syntax for initializing elements of a dynamic array using a non-default constructor.

You have to create the array first, then loop over the elements and assign each individually. Possibly the simplest way to do that is to use std::fill .

Answer 2

Array of books is a one dimensional array and it should be defined as follows:

library(int x)
{
        arrOfBooks = new book[x];
};

If you have an assumption all books have same page you have pass it as a default parameter to your book class constructor:

book(int i=200)//set the defautlt value here
{
    numOfPages = i;
};

Answer 3

Using templates:

#include <iostream>

template <int book_capacity> class book
{
private:
    int numOfPages;
public:
    book(): numOfPages(book_capacity){}
};

template <int lib_capacity, int book_capacity> class library 
{
private:
    book<book_capacity> arrOfBooks[lib_capacity];
    int cnt;
public:
    library(): cnt(0) {}
    void addBook(book<book_capacity> b)
    {
        if (cnt < lib_capacity)
        {
            arrOfBooks[cnt] = b;
            cnt++;
            std::cout << "book is added" << std::endl;
            return;
        }

        std::cout << "library is full" << std::endl;
    }
};

int main() 
{

    library<2, 4> lib;
    book<4> b;

    lib.addBook(b);
    lib.addBook(b);
    lib.addBook(b);
    lib.addBook(b);

    system("pause");
    return 0;
}