为什么这种情况发生在向量中

我一直在编写代码来将书籍添加到图书馆。当我将书籍添加到图书馆并尝试显示它时，图书馆中没有存储(显示(任何内容

在这里，我将图书馆可以容纳的最大书籍数量设置为 100。
整数最大书籍=100; 矢量迷你图书馆(最大书籍(; 但是，当我擦除"(最大书籍("时，代码工作正常。但我没有 明白为什么吗？

#include <iostream>
#include <vector> 
#include <string>
using namespace std;
//struct model a book 
    struct book {
    string authorname;
    string bookname;
}; //struct ends here 
//function to display number of books in the library
void displayLibrary(vector <book> &cmini_library,int cnum_of_books);
//function to add books to the library;
void add (vector <book> &cminilibrary,book dummylibrary,int &num_of_books);
int main() {
    int option;
    int curr_num_of_books = 0; //current number of books in the library
    int maxbooks = 100; //max number of books our library can hold 
    vector<book> minilibrary(maxbooks); //minilibrary vector of max capacity 100
    book dummylibrary; // a variable used to hold entries for a short period 
    cout << "1.Display all books in the library" << endl;
    cout << "2.Add a book to the library" << endl;
    cout << "option entered: " << endl;
    cin >> option;
    switch (option) {
        case 2:
            add (minilibrary,dummylibrary,curr_num_of_books);
            displayLibrary(minilibrary,curr_num_of_books);
            break;
        }
    return 0;
}
void displayLibrary(vector <book> &cmini_library,int cnum_of_books)
{
    for(int i=0;i<cnum_of_books;i++) {
        cout << "Book name: t" << cmini_library[i].bookname << endl;
        cout << "Author: t" << cmini_library[i].authorname << endl;
    }
}
void add(vector<book> &cmini_library,book dummylibrary, int &num_of_books) 
{
    int booksadded=0; // number of books added to the library
    cout << "How many books do you wish to add: ";
    cin >> booksadded;
    cin.ignore(1,'n');
    for(int i=0;i<booksadded;i++) {
        cout << "Book name: ";
        getline(cin,dummylibrary.bookname); 
        cout << endl;
        cout << "Author: ";
        getline(cin,dummylibrary.authorname);
        cout << endl;
        cmini_library.push_back(dummylibrary);
    }
    num_of_books = num_of_books + booksadded;
}