C++ overloaded operator []

Question

I have made a application where you type the amount of books you want to enter and using overloaded operator ([]) but every time I give a pointer to store an array, it gives me an errors such as

2 IntelliSense: expression must have integral or unscoped enum type Line:11 Column:24 Library Books

and

Error 1 error C2440: 'initializing' : cannot convert from 'std::string' to 'unsigned int' Line:11 Column:1 Library Books

but anyway here is my code:

#include <iostream>
#include <string>
using namespace std;

class Books{
private:
    string* storage;
    string book;
public:
    Books(){
        storage = new string[book];
    }
    void savebooks(int iterate){
        for (int i = 0; i < iterate; ++i){
            cout << "Book: ";
            getline(cin, storage[i]);
        }
    }

    const string operator[](const int ref){
        return storage[ref];
    }
    ~Books(){
        delete storage;
    }
};

int main(){
    //local variables 
    int quantity;
    //user display
    cout << "Welcome to Book Storage Viewer" << endl;
    cout << "How many books would you like to insert: ";
    cin >> quantity;
    //instantiante 
    Books bk;
    //other handle
    bk.savebooks(quantity);
    //display books
    cout << "These are the books you've entered" << endl;
    for(int i = 0; i < quantity; ++i){
        cout << bk[i] << endl;
    }
    system("pause");
    return 0;
}

also I am not 100% sure if I have coded this correctly and if there are anymore errors please tell me and thanks.

Answer 1

This statement

    storage = new string[book];

is invalid. The subscript value shall have integral or unscopped enueration type.

It seems your class definition has a typo and instead of

string book;

there should be for example

int book;

I think you meant the following

private:
    string* storage;
    int quantity;
public:
    Books( int quantity) : quantity( quantity ) {
        storage = new string[this->quantity];
    }
    void savebooks(){
        for (int i = 0; i < quantity; ++i){
            cout << "Book: ";
            getline(cin, storage[i]);
        }
    }
//...

And in main there should be

int quantity;
//user display
cout << "Welcome to Book Storage Viewer" << endl;
cout << "How many books would you like to insert: ";
cin >> quantity;
//instantiante 
Books bk();
bk.savebooks();