如何在此实现搜索？

Question

我已经满意地处理了选项 1，所有其他选项都悬而未决。 我已将新书附加到文件末尾，但是我无法在现有书籍中搜索查询。我也没有正确的代码来处理发行一本书并将其从记录中删除并将其删除到 students.txt 文件中。

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

int main()
{
int choice;
cout<<endl<<endl<<"       ***************|Central Library Welcomes you|***************       "<<endl<<endl<<endl;
cout<<"       What would you like to do today:"<<endl<<endl;
cout<<"       1. Add a new Title."<<endl;
cout<<"       2. Search."<<endl;
cout<<"       3. Issue a book."<<endl;
cout<<"       4. Return a book."<<endl;
cout<<"       5. Student records."<<endl<<endl;
cout<<"       Please enter your query here:";
cin>>choice;
cin.ignore();

//for adding a new record. Works Fine. So far. I have added the app mode so that it enters new records at the end rather than deleting the whole file.
if (choice==1){
cout<<endl<<endl<<endl<<endl<<endl<<endl<<endl;
cout<<"       Please enter the name of the book."<<endl;
string name;
cout<<"       ";
getline(cin, name);
cout<<endl<<"       Please enter the name of the author."<<endl;
string author;
cout<<"       ";
getline(cin, author);
ofstream addbook;
addbook.open("library.txt", ios::app);
addbook<<"NAME: "<<name<<endl<<"AUTHOR: "<<author<<endl<<endl;
addbook.close();
}


if (choice==2){
string search;
ifstream openFile;
openFile.open("library.txt");
cout<<endl<<"       Please enter the Keyword you will like to search for."<<endl;
bool isFound = 0;
cout<<"       ";
getline(cin, search);
if (openFile.is_open())
{
    while (!openFile.eof())
    {

    //The search should go here. I want to return the whole record if the search was successful. 


    openFile.close();
}
}
}
if (choice == 3){
    ifstream issuebook;
    issuebook.open("library.txt");
    cout<<endl<<"       Please enter you name."<<endl;
    string sName;
    cout<<"       ";
    getline(cin, sName);
    cout<<"       Please eneter the name of the book you will like to issue."<<endl;
    string bookFind;
    cout<<"       ";
    getline(cin, bookFind);
    //here we have to find the book in the file and remove its records from library file. 

    issuebook.close();
}
//CHOICE 4. This will take the name of the author and book and add it back to the library.txt file.
if (choice == 4){
    string returnedBook;
    string authorName;
    cout<<endl<<"       Please enter the name of the book you would like to return."<<endl;
    string name;
    cout<<"       ";
    getline(cin, name);
    cout<<endl<<"       Please enter the name of the author."<<endl;
    string author;
    cout<<"       ";
    getline(cin, author);
    ofstream addbook;
    addbook.open("library.txt", ios::app);
    addbook<<"NAME: "<<name<<endl<<"AUTHOR: "<<author<<endl<<endl;
    addbook.close();


}

if (choice == 5){
    ifstream studentRecords;
    studentRecords.open("student.txt");
    cout<<endl<<"       Enter the name of the student you will like to search for:"<<endl;
    string student;
    cout<<"       ";
    getline(cin, student);
    //Display the record of student.

    studentRecords.close();
}
}

Answer 1

您应该做的第一件事是为书籍定义数据结构。比如：

struct Book {
    std::string name;
    std::string author;
    std::string ISBN;
}

然后你可以重载输入和输出操作符

std::ostream& operator<<( std::ostream &o, const Book& b) { 
     o << b.name;
     o << b.author;
     o << b.ISBN;
     return output;            
}

和

std::istream& operator>>( std::istream& in, Book& b ) { 
     in >> b.name;
     in >> b.author;
     in >> b.ISBN;
     return in;            
}

一旦你有了这个，你就可以使用任何输入流或输出流（例如std::cout/std::cin或ifstream）来读/写一本书，例如

Book b;
std::cin >> b;
std::cout << b << std::endl;

其实你的问题太笼统了，我只能给你一些提示。您将不得不从您的讲座或一些书籍中学习所有这些。但是，如果我是一名教师，以上是我要教的关于 C++ 的第一件事。